as sis textbook answersav

AS Science in Society

AS Science in Society answers to chapter 1 questions

page 1

AS Science in SocietyAnswers to the questions

Chapter 1 The germ theory of disease

The answers suggested here should not be read as model answers. They are intended to indicate a possible approach. In some cases, information and comments are included which go beyond the direct requirements of the question.

1 and 2 Semmelweiss factors and observations: the people delivering babies (medical students seemed more likely to cause the disease than midwives),

the other activities of the people involved (the main difference between these two groups of carers was that medical students also dissected corpses),

contamination on the hands of the people (medical students moved straight from dissection to delivering babies). the role of hand-washing in preventing infection (he found that the more careful and frequent the doctors hand-washing the less the infection of mothers).3 Semmelweis suggested that an infectious agent found in corpses might be transmitted to patients through cuts.4 Chlorinated lime is an effective disinfectant; it kills the germs carried on the doctors hands.

5 Examples:

hand washing before eating, before preparing food, and after using toilet;

washing fruit and vegetables; keeping food cold;

keeping food covered.

6 Semmelweiss was young and inexperienced. He was proposing a significant change in accepted practice. People seldom change their minds easily unless they have enormous respect for the person suggesting the change. Scientific evidence alone is very slow to change ideas. Semmelweisss experience is in contrast with the rapid acceptance of Pasteurs ideas 10 or 15 years later because Pasteurs reputation had already been established.7 Preventive measures are very effective in reducing the incidence of infectious diseases such as puerperal fever. However there is almost always a need for curative measures as well, to treat the few cases which still occur. Antibiotics, the only cure for puerperal fever, were only introduced in the 1950s. Until then a few women continued to die.

8 In developing countries many women give birth at home, assisted by a traditional birth attendant. They have very little clean water so even if they understand the importance of hygiene it is difficult to achieve. But also many people who have had little or no education still use traditional practices, which may actually introduce infection. Instruments are not sterilised, local materials such as dung or plant material may be applied to the woman. In many areas the nearest medical services may be too far away.

Education and training for local traditional midwives is probably the most important way of preventing these deaths. But the midwives also need more access to sterile equipment, antibiotics and clean water as well as support from medically qualified staff if there are complications.

Answers which suggest that all women should give birth in modern hospitals reflect a lack of awareness of the reality of life in the rural areas of developing countries.

9 Lack of either sanitation or rubbish disposal made the air smell bad. This led to the theory that the bad smells given off by any decomposing organic matter or rotten flesh could cause disease. The theory explained the well known association between unhygienic living conditions, and rates of infection. 10 a) Chadwick believed that the smells in the air caused the disease. He therefore predicted that reducing smells by removing sewage would reduce disease.

b) By washing all infected sewage into the Thames, he actually spread cholera because at that time, many people all over London used water taken directly from the Thames. Drinking infected water is a very effective way of catching cholera.

11 If the infectious agent multiplied in an infected person it would explain how the disease developed in the individual. But even more important, it explained how one infected person could supply enough material to infect a large number of other people.

12 Snow showed clearly that there was a correlation between the water supply and the incidence of cholera. He was not able to demonstrate a causative agent actually in the water. He was not believed because people were unwilling to believe in germs that they could not see, smell or taste. They wanted more evidence before overthrowing an existing theory.13 One way was by mapping the homes of all the people who got cholera and showing that they all got their drinking water from the same source.Secondly, he collected data to show that the prevalence of the disease depended on the water company that supplied the water.

14It was public. It worked. It was easy to understand.15 The two conflicting theories led to two different, testable, predictions for the probable distribution of cholera cases in the area. In part of South London, houses in the same street often got water from different suppliers. One of the suppliers provided clean unpolluted water, the other provided Thames water containing sewage. The miasma theory would predict that people living in the same street would breathe the same air and therefore have the same chance of getting cholera. The water-borne theory would predict that the chance of getting cholera depended on the water supply, not the air in that street. Snow found that the incidence of cholera was linked to the water supply, as predicted by his theory, but not by the miasma theory.16 A short answer is that it is easier to believe in germs once you can actually see them. Good microscopes allowed scientists to recognise differences between different organisms and to learn that the organism is specific to the particular disease.

A longer answer would require an explanation of Kochs work. Experimental work based on his postulates (http://web.ukonline.co.uk/b.gardner/Koch.htm) finally confirmed the germ theory of disease.

17 It is not possible to test every situation and therefore it is always possible that some unexpected factor could cause spontaneous generation. It is always hard to prove a negative.

Pasteur set out to show that it does not happen under any of the conditions he tested. He then made the generalisation that spontaneous generation is not possible. But all such scientific theories are provisional; they might be changed by new discoveries.18 This suggested that the infected worms contaminated the leaves in some way leaving an infectious agent behind.19 It is usually essential to demonstrate the causal agent and a plausible mechanism (in this case for infection) before a theory can be fully accepted.

20 The front line barriers to infection shown in Figure 1.11 sometimes fail. The skin may be cut; tetanus is an infection which enters the body via a cut. The respiratory system may be damaged by influenza or other disease allowing infection such as pneumonia to take hold. The stomach acid is ineffective against some microbes, particularly if they are present in large numbers. Salmonella from infected food enters this way.

The second line of defence, the immune system, usually deals with microbes if they do enter the body. However, the immune system is sensitive to the overall health of the body and malnutrition, or another infection, can make it less effective.

21 Death from any disease may be due to a failure of either prevention or cure.

The most important methods for prevention of cholera are the provision of clean water and effective sewage treatment and disposal. In Low Income countries, neither of these measures are widely available, so once one person is infected, the disease is able to spread rapidly. This is a particular problem when people are crowded together as they are in refugee camps.

Death from cholera is due to dehydration rather than the toxicity of the bacteria, and it is often possible to cure the patient if they drink large quantities of clean water containing salts and sugar. Nowadays, health workers are all taught about the importance of this Oral Rehydration but not everyone who gets cholera is cared for by someone with this knowledge.

Children are particularly vulnerable because their immune systems are less developed. They may also take less hygiene precautions.

22 The cartoon in Figure 1.14 shows that people were frightened of having the smallpox vaccine because it was derived from cows (as the name vaccination indicates). They thought that somehow features of the cow would be transferred to their bodies. Many people still have exaggerated fears of vaccination but the symptoms they fear are different. See p 21 for examples. 23 a) As part of Jenners medical practice, he made observations and heard information from local farmers about how cowpox protected against smallpox. He also knew that one attack of smallpox, if survived, meant that you would never catch it again. This led him to the hypothesis that deliberate infection with cowpox would give protection against smallpox.

b) and c) Jenner predicted that if someone were infected with cowpox they could later be safely exposed to smallpox. The only way to find out whether his hypothesis was correct was to test the prediction experimentally. He did this by infecting a small boy with cowpox, taking some pus from cowpox spots on a milkmaid and scratching it into the boys skin. When the child had recovered from the mild cowpox illness, he deliberately infected him with smallpox, taking some pus from a smallpox spot and scratching this into the boys skin. The prediction was confirmed. The boy remained healthy.

24 Not all experiments work as planned. Most people, like the assistant, would have just put this one down to carelessness and ignored it. They were not looking for a vaccine at the time but Pasteur knew about Jenners work and recognised how important the technique would be if it could be applied to other diseases. Somehow, he made the connection in his mind between a batch of chicken cholera which was less serious than usual, and the cowpox. He had the ability to link a chance observation in one set of experiments to a different problem he had already been thinking about.25 Although by this time, 1879, more and more evidence was accumulating in favour of the germ theory of disease, there were still many people like Rossignol who did not believe it. Pasteurs anthrax experiment provided scientists with important confirmation of the theory. The technique was developed using predictions made by the germ theory. It would have been hard to explain the results using any other theory.

It also helped acceptance by the public. This demonstration was easy to understand. The vaccinated sheep lived, the others died. Because anthrax was a major problem for farmers, the results of the experiment were widely publicised. 26 a) This story is one of several which do not show Pasteurs personality in a very good light. He was a competitive and ruthless man.

Unfortunately, because he was the acknowledged expert in the field, people trusted his verdict on Toussaint. Peer review does not always work.

b) The loss of new ideas and the discouragement of young scientists in this way must slow down the development of scientific knowledge.

27 Similarities: the basic principle, of controlled exposure of the body to a microbe to stimulate the immune system, was the same in all three cases.

Differences: Jenner did not need to find a way of weakening the smallpox virus because he used a naturally occurring disease, cowpox, which was less serious but similar enough to provide immunity. For most diseases there is no such mild but similar disease, and a vaccine is a microbe weakened by treatment in the laboratory. The discovery of ways of doing this is one of Pasteurs important contributions to medicine.

The research work leading to the use of the vaccine was also different. Pasteur, working eighty years later, tested his vaccines in more carefully designed experiments, using controls. Whereas Jenners first trial was on a small boy, Pasteur tested his vaccines on animals before they were used on humans.28 Points which might be used in the argument to support Pasteurs decision include: he had tested the vaccine in dogs; the patients or their parents had given consent, even begged him to do it; he discussed the decision to treat humans with his colleagues, including doctors. Although not all those bitten do die, the chance of doing so was 1 in 6 (16 in 100), a high risk. As he continued to treat humans, the statistics began to confirm that the vaccine greatly reduced the risk of developing the disease.

Points which suggest he should have spent more time developing the vaccine include: the fact that it had only been tested on about 50 dogs and on no other species; he did not fully understand how his vaccine worked. (Rabies is caused by a virus and could not therefore be seen or grown outside living tissue.) Today Pasteur would not have been allowed to use his vaccine on humans until he had spent far more time developing it. (The same conflict between adequate testing and immediate need for medical care still arises today.)29 All new scientific claims should be confirmed by being repeated in a different laboratory by different workers. There is always the possibility that the work cannot be repeated because the original results depended on some unknown local factor or even on fraud.

30 a) Cells: Kochs work to identify and distinguish the cells of bacteria that cause disease.b) Microbes: Snows theory about invisible infectious agents; Kochs identification of bacteria that cause disease; Pasteurs study of fermentation and experiments to show that spontaneous generation does not happen.

c) and d) Immune system and protection by infection: longstanding practice of immunisation against smallpox in Turkey disseminated by Lady Mary Wortley Montagu; the work of Jenner with cowpox and Pasteur with anthrax and rabies.

31 a) Correlation: between dissecting corpses and puerperal fever; between drinking water from a particular source and infection with cholera; between infection with cowpox and being resistant to smallpox.b) Controlling factors: Pasteurs experiments with silk worms and his classic swan-necked flask studies of fermentation.c) Plausible mechanism: Kochs work to identify bacteria and to show that particular germs cause particular diseases; Pasteurs demonstration that he had isolated and cultured the bacterium that causes chicken cholera.d) Theories involving invisible objects: Snows theory of there being an infectious agent in contaminated water.e) Imagination and conjecture: Snows theory of the cause of cholera at a time when the miasma theory was dominant; Pasteurs recognition of the significance of a failed experiment.f) Testing predictions: Jenners prediction of the results of inoculation with cowpox; Pasteurs vaccination experiments notably with anthrax.g) Influence of earlier work: the influence of Jenners work on Pasteur who decided to extend the idea beyond smallpox to other diseases.h) Desire to be first with a discovery: notably Pasteur in all his work.AS Science in Society

Answers to the questions

Chapter 2 Infectious diseases now


1 It is easier to believe in germs once you can actually see them. Good microscopes allow you to recognise differences between different organisms, and to learn that the organism is specific to the particular disease. More powerful microscopes also make it possible to probe the internal structure of microbes and understand how they cause infection.

2 Bacteria start reproducing as soon as they enter the body and multiply at a steady rate by cell division. As the number of bacteria in the body increases, the symptoms become worse.

A virus has to enter a cell in the body and use the mechanisms of the cell to reproduce. Whilst the viruses are growing inside cells there will be very few symptoms. Once the cell is full of viruses it bursts. The symptoms of the illness are usually caused by this sudden cell damage. The viruses go on to invade new cells and the symptoms subside until the next wave of cells burst.

3 Semmelwiess observed that childbed fever was spread by doctors or medical students going directly from one patient to another, or from the dissecting room to the patients. The medical students did not become ill but a doctor died from the same symptoms after cutting himself during dissection. The explanation for these observations is that the germs from a corpse or an infected person can be transmitted by contact but only enter the body through cuts or wounds, common during childbirth.

Snow observed that cholera infection seemed to be spread by contaminated water. The explanation is that the bacteria are excreted in the diarrhoea of a sick person. If this is allowed to contaminate drinking water then the bacteria will be swallowed and may cause infection.

4 The most straightforward way of showing the causal link would be to devise an experiment whereby some people were exposed to the disease by the proposed method of transmission and to then compare their rate of infection with that of a control group. However in most cases, this would be totally unethical. This technique could be used on animals if there is a species which is susceptible to the same disease.

The other important method used is to isolate the infectious organism, to identify this organism in the ill person in every case of the disease and also in the transmission route. The discovery of the malaria trypanosomes inside mosquitoes as well as in malaria patients was a vital step in understanding the transmission of malaria.

To show that Staphylococcus infections are transmitted in hospital bedding, it would be necessary to find the same strain of bacterium in the bedding as in the patient. This by itself might be due to common cause and it would also be necessary to show that killing the bacteria in the sheets reduced the transmission rate to patients.

5 Transmission by living creatures: destruction of habitats of carriers of disease; eradication programmes with pesticides.

Infection from clothing or bedding: use of disposable alternatives in hospitals; inspection to ensure high standards of hygiene in the handling and laundering of fabrics.

Direct skin contact: provision of low cost barrier prevention such as condoms; access to diagnostic guidance from local pharmacies, on-line services and primary health care.

Coughs and sneezes: public education along the lines of coughs and sneezes spread diseases; quarantine programmes in extreme cases.

Contaminated food and water: water and sewage treatment; regulation supported by inspection to ensure appropriate high standards in all places where food is stored, prepared and served.

Infection through cuts: provision of access to first aid and primary health care; public health education about the risks.

6 Mass vaccination for all children is compulsory in some European countries.

It is well known that a few people can opt out of vaccination for their children without risk of infection as long as the majority, about 95% are vaccinated. However, if too many people come to rely on others to take the small risk of vaccination in this way, infection will spread.

There is an important principle of the need for consent before any medical procedure is carried out. Compulsory vaccination ignores the families rights to give or withhold consent.

This issue is discussed in a report from the Nuffield Council on Bioethics which uses vaccination as one of the case studies to explore in Public health: the ethical issues. See chapters 2 and 4 in the report which can be downloaded at: www.nuffieldbioethics.org/go/ourwork/publichealth/publication_451.html.

7 Fleming is famous because he was the first person to recognise an antibiotic and its potential against bacteria and therefore did the most original work.

Some would argue that Florey and Chain should be given equal credit because they were the ones who really recognised the significance of the discovery, and actually developed useful penicillin production. Others would say that their contribution, though important, was less original. In 1945 all three received a Nobel Prize for the work.

8 a) The more often bacteria are exposed to an antibiotic, the more likely they are to become resistant. Doctors do often prescribe antibiotics when they are not strictly necessary. Antibiotics are useless against diseases caused by viruses. Patients expect to get antibiotics when they are ill whether they need them or not.

b) The problem of antibiotic resistance was not appreciated when the drugs first became available. It was very hard to restrict the use of drugs that were so effective.

c) If the use of antibiotics were restricted to situations in which they are absolutely essential, resistance would take much longer to develop. Prescribing policies of hospitals and primary care centres could be stricter and more tightly monitored.

9 TB is airborne therefore close contact increases the rate of transmission of the disease. Improved housing and working conditions reduce overcrowding and transmission of TB.

Even with improved housing, it is likely that most people are exposed to the TB bacterium at sometime. When their nutrition is good their immune system is usually able to protect them against the infection and the bacteria will lie dormant in the body. Better nutrition is therefore one of the most important improvements in social conditions.

10 The differences between the UK and countries where TB is still widespread are almost entirely due to income. Many countries of the world do not have the resources to provide adequate housing and living conditions. They may be unable to pay for, or organise an immunisation programme to give BCG to all children. Many of the people may be too poor to afford an adequate diet.

11 a) Data on the number of deaths is usually more reliable because all deaths must be recorded and a cause of death given on the death certificate. Tuberculosis is a notifiable disease, which means that doctors have to inform the government of any cases they diagnose. Notifications are probably fairly accurate except that not everyone who is ill goes to the doctor. In both cases the figures will not be 100% reliable, particularly the earlier ones, because accurate diagnosis of the cause of illness or death is not always possible.

b) Less crowded living and working conditions, pasteurisation of milk and control of spitting in public places all reduced transmission of TB. Improved nutrition meant that even if someone was infected, they were much less likely to become ill and infect others.

c) All the changes mentioned in (b) above contributed to the decline in incidence of TB. This was before the introduction of the BCG vaccine or of any medical cure for TB.

d) 1940 to 1950 is the period during and immediately after the Second World War (1939 1945). During the war, many people had to spend time in crowded conditions, in military camps and in air raid shelters. Because it was difficult to import food, nutrition standards may have declined.

e) Mass X-ray screening meant that those with TB could be diagnosed and therefore treated and cured at an earlier stage in the illness. They would thus infect less other people. The mass X-ray programme has ended because there are now so few cases of TB in the UK that it would detect very few new cases of TB. The programme is expensive and no longer cost-effective. Nowadays the same money would contribute more to the health of population if spent in other ways.

f) Fig 2.16 shows the drop in notifications between 1915 and 1950 as around 40 000. This indicates just how effective preventive measures such as reduced crowding and nutrition are.

Between 1950 when both chemotherapy (cure) and BCG (prevention) were introduced and 1990 the drop is also around 40 000. Cure does reduce notifications because, as mentioned in (e) above, one persons cure is anothers prevention. On the basis of figure 2.16 it is hard to be sure whether chemotherapy or BCG is the more significant in preventing the spread of TB as they were both introduced around the same time. Other information not given here shows that overall preventive measures such as BCG and nutrition are much more effective than curative measures.

12 TB affects people in the 15-54 age range when they are most economically productive. People with TB have to take months off work. This means that where TB is common, there are many people and families that are likely to be poor.

13 Political commitment is important because an effective TB control programme requires organisation, trained personnel, money, and the support of the whole population.

14 Patients may find it hard to continue taking the drugs when they are apparently cured. They need time to collect the drugs, there may be side effects and they may simply forget. However, to ensure that the disease will not recur and to reduce the risk of drug resistance, it is vital that treatment continues. Supervision does improve compliance with the treatment regime. Surveillance is an infringement of the rights of the individual in their own best interests, and in the interests of the wider community. A decision on this will depend on cultural and political values.

The most desirable outcome would be that people were given enough scientific understanding and support to be prepared to continue the treatment voluntarily.

15 a) As discussed in question 14, people may stop taking the medicine too soon for a range of reasons. This, and the use of a single drug rather than a mixture of several anti-TB drugs are the main reasons why resistance develops.

b) Worldwide measures which might have prevented resistance developing are important because diseases spread readily from one region to another. The World Health Organisation, WHO, has now drawn on experience from all over the world to devise a strategy for TB treatment which is designed to reduce the development of resistance. It provides advice and financial support to put the strategy into practice. The strategy is given at the bottom of page 28.

16 Poorly supervised TB treatment might lead to widespread development of drug resistant strains of TB. For individual patients, any treatment is still better than no treatment but the rights of the individual may conflict with those of the society, for whom drug resistance is the greater danger.

17 In some countries where TB is widespread, there are people outside the reach of health care agencies. The resources do not exist to carry out tests on all the people who might have TB. The problems are discussed in the report on this WHO web page:

http://www.who.int/tb/publications/global_report/2008/download_centre/en/index.html18 Overcrowding in refugee camps. Contact between patients and a larger total number of people. The long-term treatment may be interrupted by displacement. Displaced people often find it hard to get adequate nutrition.

19 Resistance to a disease develops when the immune system is able to respond quickly to a microbe it recognises from previous exposure. Influenza is caused by a virus which mutates as it reproduces in people and in animals, forming different strains. The virus strain which infects you a few years later may have a different protein surface from the original infection. The immune system will not recognise it.

20 a) Influenza vaccines cannot be prepared more than a few months before they are needed because they have to be specific to the particular strain which is in circulation. Mutations in the influenza virus mean that a vaccine prepared more than a year earlier would be ineffective because it would only give protection against an earlier strain. This makes it hard to build up large stocks of vaccine.

b) and c) When supplies are limited, some form of rationing is essential. The priorities chosen by the Government mean that those who are most likely to die as a result of flu, the elderly or those with chronic lung disease, are protected. Health workers get protection so that they can look after everyone else.

21 Relevant factors include: intensive farming of poultry and other birds; people living in close contact with birds; extent of travel by people between countries and the trade in farm products; limited research into vaccines; limited availability of antiviral drugs in many parts of the world.

22 A vaccine has to be specific to the particular form of the virus. So development of a vaccine cannot start until the virus has been identified and isolated.

23 One approach is to make vaccination mandatory so that people do not have any choice. Another approach is public information and education to maintain awareness of the potential consequences of an outbreak of the disease. There is an ethical dimension to the discussion as explained in the report from the Nuffield Council on Bioethics mentioned in the answer to question 6:

From the first perspective, most people accept vaccines in situations in which the incidence of a vaccine-preventable disease is high, the disease is potentially serious and the risks from the vaccine are proportionately low. The situation is different where incidence is relatively low, as there may be both statistical and perceptual changes in the assessments of risks and benefits. Statistically, where there is fairly high vaccine coverage, the risks of disease for those who are unvaccinated may decrease (owing to population immunity) while the risks of vaccination remain. For example, in the USA, as a result of high levels of vaccination for measles, the risk of exposure to the disease-causing virus is very low, while the vaccine used causes fever or rash in around 5% of cases and very occasionally causes more severe reactions. Although healthcare professionals consider the risks of such trade-offs carefully, low incidence of a disease may also affect peoples perceptions of it. They may view the risks of contracting a vaccine-preventable disease not to be serious, since they are less familiar with its symptoms or severity as a result of its low prevalence (owing to a high level of vaccination coverage), and may be more likely to refuse vaccination.

24

TBInfluenza

CauseInfection by a bacteriumInfection by a virus

How it spreadsWhen people with the disease cough, spit, sneeze or talk producing droplets with bacteria in the air.Spread in tiny droplets caused by coughing and sneezing. People can become infected by touching something contaminated with the virus and then touching their mouth or nose.

Methods of preventionPublic health measures to improve living conditions and reduce overcrowding. Healthier people are less likely to get the disease. BCG vaccination which is only partly effective.Immunisation

TreatmentsCombination treatment with antibiotics.No drug to cure the disease. Antiviral drugs can help to control the symptoms.

Factors making it difficult to controlRapid development of drug resistance. Needs to sustain treatment if it is to be effective. The AIDS epidemic. HIV makes people more vulnerable to TB.Frequent mutations in the influenza viruses which means that new vaccines have to be developed each year.

Interaction between animal and human forms of the disease.

25 Technical feasibility: an effective regime of antibiotics is available for treating TB whereas antiviral drugs to deal with influenza are not yet available. Vaccines for influenza are a challenge because of the frequent mutations that change the characteristics of the virus.

Benefits expected: the potential or actual economic benefits of eliminating or reducing TB in the working population are high and justify very large expenditures on programmes to detect and cure the disease.

Economic cost: research to develop treatments for diseases that are prevalent in the poorer parts of the world can be limited by the lack of an incentive for commercial pharmaceutical companies to invest.

Risks: the risk and consequences of an influenza pandemic are so high that some governments are investing substantially in research into the development of types of vaccine and antiviral drugs.



Chapter 3 Transport issues


1 a) Elements have atoms of only one kind so hydrogen, oxygen and carbon are all elements.

b) Compounds are made up of two or more elements atoms bonded together, so carbon dioxide and water are both compounds. NOTE: The atoms do need to be bonded together to form a compound, otherwise you just have a mixture of atoms.

c) An atom is the smallest part of an element. Each element has its own kind of atom. So there are carbon atoms, hydrogen atoms and oxygen atoms.

d) A molecule consists of two or more atoms joined together. The atoms can be the same as in oxygen or different as in water or hydrocarbons.

e) A hydrocarbon is a compound made up of just hydrogen and carbon atoms bonded together.

f) A chemical reaction is what has happened when atoms and molecules rearrange themselves to form new substances. Here it is illustrated by having the hydrocarbon reacting with the oxygen to form carbon dioxide and water. The number of each type of atoms is the same after the reaction as before, but the atoms are arranged differently.

g) Combustion is a reaction between chemicals and oxygen, resulting in the release of energy. Here it is the reaction between the hydrocarbon and oxygen molecules to make carbon dioxide and water.

2 Diagram similar to figure 3.4 to show one molecule of propane reacting with five oxygen molecules to make three carbon dioxide molecules and four water molecules.

3 a) The energy industries are those which supply electricity and fuels.

b) Up to 2005 there was no sign of any start of a significant decline in emissions. All sectors will have to contribute to change if the targets are to be met.

4 a) Road freight: from 15 to 22 million tonnes of CO2 equivalent - an increase of about 47% in emissions.

b) Air transport: from 20 to 37 million tonnes of CO2 equivalent - an increase of about 85% in emissions.

5 Biggest contribution is from air transport which has risen most in the period but has now started to decline. Next biggest is road freight which has increased steadily over the period. Public transports emissions have slowly declined during these years. The contribution from water transport has fluctuated but not changed greatly. (Increases in fuel costs in 2008 could have a significant impact on these figures.)

6 The energy comes from the Sun.

7 a) Plants take in carbon dioxide and turn it into sugars and other chemicals by photosynthesis as they grow. In theory, this balances the carbon dioxide given out when chemicals from plants burn.

b) Energy is needed to cultivate and harvest plants. More energy is needed to process plant material and turn it into fuels. Supplying all this energy involves the use of fuels that give out carbon dioxide.

c) There is more intense sunlight in the tropics. Plants such as sugar cane need less fertiliser and some of the energy for processing the plant material into fuel can come from burning the dried crop waste.

8 Advantages: renewable unlike fossil fuels; reduced emissions of carbon dioxide; can help to reduce reliance on imported fuel.

Disadvantages: grown on land that could be used to grow food; may be grown on land made available by destroying tropical forests.

9 The key point here is that with a fuel such as gas, the energy given out when it burns does not disappear but is still around transferred to other things. Some useful, some not so useful. Energy transferred to the environment will heat it up, although only by a tiny amount if taken globally, and some will be radiated out into space. None is lost, it is just distributed more widely. This is the principle of conservation of energy.

10 a) Start with 6500 GJ. First arrow branches off taking 2000 GJ to produce the fuel rods. Second arrow branches off taking 1000 GJ left in the spent fuel rods. Third arrow branches off showing 2400 GJ thermal energy lost to the surroundings (e.g. from cooling towers or cooling water) leaving an arrow at the end showing the supply of 1100 GJ energy as electricity.

b) Efficiency = (1100 GJ ( 6500 GJ) ( 100 % = 17%

11 Suck, squeeze, bang, blow. Note that there is not really such a process as suck in terms of a vacuum producing suction. What happens here is that the piston, in moving down, creates a partial vacuum (low pressure) inside the cylinder. This causes the atmosphere (high pressure) to push fuel into the cylinder.

12 1 kg is 1000 g. 1 mg is 1/1000 g. So each 1 kg is made up of 1 000 000 mg, hence 1 ppm.

1 mg is just a few grains of salt. You would be unlikely to be able to taste it.

13 a) Carbon monoxide and volatile organic compounds.

b) Sulfur dioxide.

c) Oxides of nitrogen.

14 Nitrogen dioxide is produced as there is plenty of nitrogen, approximately 78% in fact, in the air. At low temperatures nitrogen is inert, but at the high temperature in the cylinder of an engine it can react with oxygen.

15 If the air/fuel ratio is too low then incomplete combustion will take place leading to the release of carbon monoxide and volatile organic compounds. Carbon monoxide puts a strain on the heart in low doses and can be fatal in high doses. Unburnt fuel contributes to photochemical smog. Having too high an air/fuel ratio (too much air) results in poor ignition.

16In Summer the Sun is brighter. It is more intense and so more effective at splitting up oxides of nitrogen. This leads to the formation of ozone.

17 Rush hour traffic in the morning releases the chemicals needed to produce the smog. However, the energy from the sunlight to bring the reactions about, does not reach its peak until around midday when the sunlight is most intense.

18 a) Carbon dioxide is not toxic and does harm local air quality.

b) Carbon dioxide is a global pollutant contributing to the greenhouse effect and climate change.

19 The distributions predominantly reflect centres of population and industry.

20 Emissions of PM10s has declined markedly. There have been significant declines in all sectors apart from agriculture and waste, industrial processes and road transport.

21 Nitrogen dioxide near power stations, in large cities, adjacent to motorways, next to incinerators and steel works.

Carbon monoxide near motorways and in large cities.

22 The commercial, residential and institutional contribution has fallen the most. The contribution from public power has fallen significantly too. Factors such as boosting efficiency and reducing waste bring about a reduction in the usage of fuels and hence of PM10 emissions. The use of coal in power stations has declined. Improvements in diesel fuel and the design of diesel engines has helped to cut the emissions from road transport since the 1980s.

23 1970: 8%

2004: 23 %

24 (a) It could be a one-off high reading caused by a particularly poorly tuned engine on a lorry, or one taken at a time when few vehicles are in use (Christmas Day). The wind direction might be blowing pollutants away from the detector. The extent of pollution may vary with height above road level.

(b) They can take lots of readings and average them, so reducing random errors. They can also check the readings with another instrument and confirm the data if the readings agreed. They can also check the calibration of the instruments used to ensure that the readings are accurate.

25 It is likely that the mechanism of sampling would cause the largest errors due to factors such as:

(i) the position of the detector having an effect it might be shielded from pollution or be at a place where air movement is minimal and so pollution maximised.

(ii) depending on the device used to detect and measure, there might be absorption of pollutants on the walls of the inlet tube, or reactions between pollutants en route to the detector.

Analysis of the results is more likely to be mechanised, or through a standard technique, and so is less likely to produce errors.

26 They would probably be most reliable from a power station which would come under statutory controls and monitoring. Similarly for a number of industrial processes where there is potential for pollution of the environment. Estimates for vehicles with diesel engines are likely to be the least reliable, varying for different vehicles, being dependent on age, size, and maintenance and so on.

27 a) Graph (b) appears to give a strong correlation as one could draw a line through the points. Graph (a) has cities H and T off-line.

(b) The two graphs do show that there is a strong tendency for the Death Rate Ratio to increase with increase in the concentration of particulates.

28 The findings were a potential threat to the energy and transport industries. The findings could be used as evidence to support stricter regulation of emissions which some might want to avoid.

29 Monitoring the health of a group of people for 20 years is very hard to achieve. Keeping track of all the people is difficult. It is also hard to keep the team of researchers together and to maintain funding for the research, which is expensive.

30 a)The key point here is that we breathe in from the atmosphere so what pollutes it has the potential to pollute us. The pollution does gradually disperse or get washed from the atmosphere by rain but in city streets it can be contained concentrated so that it reaches hazardous levels.

b) The particulates must build up to some extent, then get breathed in or fall to the ground or into the sea. They have not disappeared. Similarly the various gases do not disappear, though they may be absorbed or react to form something else e.g. SO2 and NO2 can both combine with water and oxygen to form acid rain.

c) Wind disperses pollutants. Rain washes some pollutants from the air. High pressure conditions mean little wind and this can trap pollutants so that they build up to unusually high levels.

31 Looking at the elements involved in figure 3.20 it is seen that those coming from the engine carbon, oxygen and nitrogen also emerge into the air but recombined to make new chemicals that are less harmful to health.

32 The catalyst used in a car exhaust system only works properly when hot. On a short journey it is unlikely to get hot enough to do its job properly.

33

Power supplyAdvantagesDisadvantages

Petrol engineProven technology. Reliable. Powerful so fast. Fuel widely available. Long range.Use of fossil fuel which is becoming increasingly expensive. Emission of carbon dioxide.

Electric motorNo emission of air pollutants by the vehicle.Limited range. Limited power. Charged by electricity from conventional power stations.

Hybrid engineNo emission of air pollutants by the vehicle when running on battery. Benefits as for petrol engines outside towns and cities.Less fuel-efficient overall. Expensive because of the need for two power sources.

Fuel cell (hydrogen)No emission of air pollutants by the vehicle.Technology not yet fully developed. Lack of widespread supply of fuel (hydrogen). Fuel still derived from fossil fuel.

34 Currently electric vehicles are charged with mains electricity. The pollution, if any, comes from the power stations. If charged at night, much of the base load comes from nuclear power. Nuclear power has relatively low emissions of greenhouse gases. However the power may also come from gas/oil fired power stations or from renewables such as wind turbines.

35 a) and b) Many factors reduced the amount of walking and cycling in this period: the relatively low cost of private transport, the increased perception of the dangers to pedestrians and cyclists (especially children), the design of towns and cities to make motoring easier and walking or cycling less attractive.,

36 This can simply be answered by comparing the lengths of the horizontal bars for each form of transport in figure 3.24.

a) Train and bus.

b) Aeroplane

c) If the car is carrying more than just its driver.

37 The problem here is that the mass of the driver and passengers is relatively small compared to that of the car. Most cars have a mass of around 1000 kg. The average mass of a person might be around 85 kg. So most of the fuel is being used in moving the car and not its occupants. Also, much of the power of the engine is used to overcome the air resistance and rolling resistance of the tyres as the car travels along.

38 There is an energy cost to creating the materials and manufacturing any vehicle. It takes a lot of energy to create trains, buses and aircraft. Therefore having them last longer reduces their rebuild energy costs and hence their lifetime fuel costs.

39 The smaller and lighter car would need less fuel and so that should reduce pollution as long as (i) their numbers did not increase and (ii) their engines were as efficient or more so than currently.

Having electric cars really moves the source of pollution from where the vehicle is used to the power station. As most power stations are built away from towns and cities, this would be practicable, but it has only replaced petrol/diesel pollution by other forms coal, oil, nuclear-based until such times as wind, solar, wave etc. become significant.

40 At the time of writing, there had been a fair amount of protesting about the high cost of fuel and the taxes on fuel and on cars that are gas guzzling. Many of those living in country areas without public transport complain at their specific situation. There is also resistance to any extension of congestion charging.

Common arguments to not bring in controls might include such matters as:

They might make the business uneconomic.

They may cause closure or promote redundancies.

Other countries do not have such controls.

They may make the business less competitive.

41 Water is a liquid at room temperature. It is a compound of hydrogen and oxygen which are both gases. Water does not burn. Hydrogen burns brightly in oxygen to make water.

Methane (in natural gas) is a colourless gas. It is a compound of carbon (a black solid) and the gas hydrogen.

42 Motoring harms health (giving out gases that pollute urban air) and the planet (giving out carbon dioxide that enhances the greenhouse effect and causes climate change). Motoring uses up scare resources: the fossil fuel that is a non-renewable resource. Extracting and processing crude oil to make fuel can cause environmental pollution at every stage.

43 Mechanical: high pressure in an engine cylinder presses down on the piston which drives the wheels through the crankshaft.

Thermal: the energy from the hot cylinder transfers to the cooling water circulation round the engine, then the hotter water is cooled by cold air flowing through the radiator.

Electrical: the battery supplies the energy to turn the motor which starts the engine running; the alternator generates the electricity to provide power to the lights and other electrical components.

Radiation: the hot filaments in the headlamps radiate light to illuminate the road at night.

44 Widespread use of catalytic converters is probably not a long-term solution as they do not in fact reduce CO2 emissions at all; indeed they probably increase them slightly as more fuel is consumed overall. The solution seems more in finding replacements for fuels that cause pollution.

Improvements in fuel and in the design of diesel engines are reducing the emissions of particulates.

Crucial to the argument is the seriousness of the health effects of particulates and oxides of nitrogen.

45 Benefits widely shared with a minority suffering the ill effects is a particular problem for air travel because of the noise and pollution concentrated around airports. In these circumstances, the interests of the minority can easily be ignored because of the wider benefits. The situation is not so clear cut with motoring. The pattern of benefits and harmful effects varies greatly from place to place depending on how close people live and work to motorways, flyovers and other places with intense road traffic.

46 a) There are still arguments about the extent to which urban air pollution is harmful to health. It is difficult to forecast what technology might be available to reduce pollution in the future. It is also difficult to predict what processes might be developed that one needs to respond to and the extent to which technology could deal with them. Similarly, it is difficult to forecast the effects of pollution long-term.

b) The social difficulties are likely to reflect the wishes and needs of the population in terms of jobs, personal freedoms and lifestyles. The political difficulties are in trying to balance what is best for the nations health and what might keep the party in office. The economic difficulties would include how tackling air pollution might affect jobs and profitability.

47 Driving less far might be realistic when employment is more local or actually working from home. Currently far from all jobs can be home-based so it is not realistic. Some never will be sales staff who need to show off goods and discuss matters with potential buyers.

Possible restrictions might include more limited access to towns and cities and promotion of Park and Ride schemes. Additional road tolls, or even a bar on some roads, when not carrying passengers. Taxing according to the number of miles travelled higher road fund tax for greater usage. Already, insurance companies are discussing having higher charges for those that use their cars the most much like the higher tax suggestion although for a different reason, namely to reduce their risk.

48 For private cars one could add a tax to petrol or have a variable road fund tax according to the miles covered. With public transport the cost could be incorporated in the charge for a ticket.

Why not make the person being moved pay? Should it apply to doctors, nurses, fire-fighters? Who else might you wish to exempt?

49 a) When choosing an upper limit, the factors to consider involve the health and environmental effects of the pollution. Also it is necessary to take into account the various costs of lowering the limits such as the impact on industries that create wealth and employment, and the value that people put on easy access to various forms of transport. Even if the lowering of emissions is feasible, it can be too expensive to be affordable.

b) The limits have to take into account the accuracy of the methods of measurement. They also have to take into account that the cost of ensuring a total absence of pollutants would be extraordinarily high or require a very dramatic change in current lifestyles.

50 Policy needs to take into account different interest groups in cities and in rural areas and consider the concerns of elderly people and those with physical handicaps or other special needs. A powerful but popular policy is to raise the cost of transport of all kinds. Another approach is to shift the balance of investment towards forms of getting about that do not involve fuels, so favouring walking and cycling as much as possible. A shift from private to public transport can cut fuel use. Congestion charging, bus lanes and investment in new buses and trains can encourage more people to use public transport. In the longer term, policies can reduce the need for travel by encouraging people to live nearer to where they work and by cutting down on the travel for shopping expeditions and so on.AS Science in Society


Chapter 4 Medicines to treat disease


1 Plants vary slightly in their chemical composition. There may be several chemicals in a plant that are chemically active. Drug developers need to know which chemical is responsible for any effect. The results of tests are very hard to interpret if they are based on mixtures of drugs of uncertain composition.

2 a) It is generally impossible to create a drug that cures a patient by interfering only with the natural processes in an microoganism or in the diseased cells of the patients body. If the drug has any effect on healthy parts of the body there are likely to be side effects.

b) Deciding whether or not a drug is adequately safe is a matter of judgement which involves weighing up the benefits and making sure that they outweigh the risks. What counts as adequately safe is not the same for a drug to treat a common cold and a drug to treat serious heart disease or cancer. No drug is without risk, but, through animal and clinical drug trials, the potential risks and benefits are measured scientifically.

3 Safety tests to check that the new drug does not harm embryos, fetuses and babies incuding tests to see if the drug passes through the placenta to the babys blood stream or gets into the mothers milk.

4 a) and b) Some interactions between drugs and chemical reactions in cells are specific to a particular species, and even to individuals within that species. Animal models and computer modelling can give useful predications of efficacy and safety, but can never predict the full potential interactions between drugs and the human body.

5 a) Phase II trials normally test the drugs on healthy volunteers so it does these people no harm to be given a placebo. Patients involved at this stage have given their consent to taking part in this phase of the testing. Testing is small scale and short term.

b) Phase III trials are carried out with large numbers of patients who are ill and need treatment. It would not be right not to give them any treatment as part of an experiment. At this stage the aim is to confirm that the dose levels are right and that there are no undetected side-effects.c)

When there is no known effective treatment available.

Where the disease is minor.

6 a) In this phase the whole population is made up of all the people with the disease that the new medicine is designed to treat or cure.

b) Doctors are likely to be more aware of patients with are more severely ill so that they have sought treatment or gone to hospital. Some people with the disease may not have seen a nurse or doctor. They may have sought help anonymously on-line or from NHS Direct. Also some patients, or their relatives may be unwilling for them to take part in a trial.

7 The efficacy of the active drug's treatment is the due to its active ingredients plus any effects of treatment (e.g. placebo effect). The effect of treatment by the drug is the difference between the active and the natural history groups. This can be compared with the efficacy of the treatment process alone: the difference between the placebo group and the natural history group. This is a measure of the placebo effect. The effect of the drugs active ingredient is the difference between the active and the placebo group. The use of a natural history groups allows the entire treatment process to be compared with the magnitude of the placebo effect.

8 a) Regulation is intended to ensure that the makers of medicines and doctors do not sell or prescribe drugs that are ineffective or harmful. Regulation in the UK is also aimed at ensuring that the NHS gets good value from the medicines it buys.

b) Regulators have to take into account: the results of drug trials showing the benefits of the drug in relation to any known side effects, the benefits to patients compared to other treatments (if any), the cost of the drug.

c) The MHRA assesses the efficacy and safety of new drugs. NICE carries out cost-benefit analyses to see if a new drug provides sufficient value to patients to justify its costs.

9 Some rare side effects may not become apparent until a drug has been prescribed on a large scale. At this stage is it not in the interest of the pharmaceutical company for side effects to become an issue. This makes it important that there is an independent system for collecting information about side effects from all available sources.

10 Your answer to this question depends on your experience and the people you know, if any, that have tried complementary medicine.

11 Your attitude to regulation might be affected by your view on the effectiveness on the medicines. Arguably, the more effective a medicine, the more important that it is regulated to ensure that it is not harmful and does not interact in a dangerous way with other treatments. You could also argue that the public should be protected by regulation from medicines that are ineffective. People who very ill can be so desperate that they waste their money of medicines that are ineffective or harmful.

12 Some (not all) people with allergies turn to complementary therapies as a result of dissatisfaction with conventional medicine and because increasing numbers of people and reports say that complementary medicine works. There are those who would argue that this is not only wise but scientific - having rejected one paradigm or theory (conventional medicine), the person switches to another. Others, though, would maintain that there is little good evidence that complementary therapies work and that some such treatments may be harmful.

13 Scientists value evidence about drugs the comes from systematic, epidemiological studies where the results have been published in peer reviewed journals, replicated by others and subjected to sustained critical assessment.

14 Complementary medicine is intended to work alongside conventional medicine, whereas alternative medicine can replace conventional approaches.

15 Complementary treatments may involve a relationship between the doctor and patient which means that it not possible for the whole process to be subject to a double-blind study.

Where the alternative is a treatment, both patient and doctor inevitably know whether or not they are receiving the complementary treatment (e.g. acupuncture) or the placebo (e.g. relaxing massage).

16 Setting up a regulatory system is expensive. It is only worth doing if it is demonstrably necessary to protect the public from harmful effects of incompetent/unscrupulous practitioners of hazardous treatments. With conventional medicine the powerful effect of medicines, the scale of use and their overall cost means that regulation is judged to be necessary. Our society has judged that regulation is largely unnecessary for most alternatives while only limited amounts of public money are spent of complementary medicines.

17 Bias arises if the people who agree to take part in the trial are all particularly disposed towards the treatment and if those who drop out of the trial are consistently those who are in some way unhappy or uncomfortable with the treatment. People may drop out or refuse to take part due to illness, and this could make it less likely that the results identify capture people suffering effects of the risk factor.

18 Toxicity testing with animals is used to determine the minimum single dose that can kill; also the dose which, if taken repeatedly can lead to serious of even fatal results. These, and other results are used to determine the dose to use in the first stages of clinical trials. Clearly it is very important to get the results right to avoid harming the volunteers involved in phase I trials. The approach has to be systematic so that the work can be replicated if necessary. Also all observations and measurements have to be carefully documented so that the outcomes of administering a drug can be related to the size of dose given. If, at any stage, things go wrong, the recorded evidence can be used to show whether or not the procedures have been carried out according to approved protocols. This could be particularly important if unforeseen outcomes lead to a legal challenge for damages in the courts.

19 Experience has shown that no animal trials can ever fully predict reactions to drugs in humans. Even so most people would consider it irresponsible not to carry out animal studies before human trials, as these studies can indicate toxicity and efficacy in many cases.

At a cellular level the processes of respiration, growth and cell division are very similar in all animals but there are many differences in the way that cells are organised from one species to another. Also the body organs have different relative sizes in different animals, and the way chemicals are taken up and eliminated from the body varies between species.

20 a) Systematic sampling is important to ensure that the sample is representative of the whole population of people that might be treated with a medicine.

b) Randomisation in the selection of participants to test and control samples is very important to avoid bias. Randomisation helps to ensure that both types of sample are representative of age, gender, ethnic origin, social class, life style and so on.

c) The larger the sample size the less likely it is that the results will be affected by random variations. With a larger sample it is more likely that results will be statistically significant. However there are practical limits to the size of samples used for medical research. These limits may be imposed by cost, the possibility of recruiting participants to the study and the feasibility in keeping in contact with a large group of people.

d) Research designs such as cohort studies and case-control studies include control groups. The control group usually receives a placebo or the standard treatment so that the effects of the medicine on the test group can be compared with a comparable group of people who have not received the new treatment.

21 Possible questions to consider:

Who has done this research and where do they work?

Who do the researchers work for and might there be any conflicts of interest?

How big was the study and were what type of research design was used?

Has the research been published and if so where?

Have other expected reviewed and commented on the findings?

Have the findings been replicated?

Who has provided this report is it from an independent journalist or from someone with an interest of some kind in the findings?

22 a) The processes of developing new medicines involve testing on animals and humans in ways that could be open to abuse if not carefully regulated. Powerful interests are involved in the discovery, production, marketing and prescription of new medicines. The sums of money involved, the reputations of health practitioners and the deep worries of sick people mean that there is considerable scope for misreporting and for the misuse of the resources available for health care. Also the consequences of mistakes can be very serious for both those who provide treatments and for patients. There are differences in status between doctors working on different specialism and some patients are, for various reasons, in a better position to get the benefits of new treatments than others. So this is such an intensely political field that governments see the need to regulate.

b) They have to take into account the efficacy and safety of the medicine as shown by all stages of clinical trials to see if the drug should be used at all. If the drug passes the initial tests, the regulators then have to carry out a cost-benefit analysis to see if the new treatment gives value for money in comparison with alternative treatments, or alternative uses of the resources for other kinds of health care.



Chapter 5 Ethical issues in medicine


1 The answer depends on your point of view. You might reflect on whether or not your opinion is affected to any extent by learning more about the development of drugs and the ways that animals are used in research. The important skill here is being able to recognise where your own ethical arguments fit with the different ethical frameworks that exist.

2 The organisation defending the use of animals in research is essentially using a utilitarian argument.

The animal welfare group is weighing up the rights of animals against the rights of humans while giving greater priority to human rights.

The antivivisectionists put priority on the rights of animals; asserting that it is unjust to experiment with animals and at the same time making the utilitarian point that the tests are of no value because the results with animals do not contribute meaningful results when it comes to the treatment of humans.

3 In planning research experts may be competent to judge whether the design of the research is one which will answer the question posed taking into account all the technical issues.

However there are two further questions which must be addressed and these are not medical or technical issues. The first is one of cost-effectiveness. If resources are limited should public money be spent on this problem rather than on some other need?

The second is a question of ethics. If the patient is likely to suffer some pain or other side-effects in taking part is this justified for the greater good? Is it possible to gain informed consent, what about research on small children? For the cost-effectiveness and ethical issues, which affect the whole society, it is important that those not involved in the work evaluate the issues and represent the views of a wider cross-section of the population. They may see the priorities differently from those who are committed to the research.

4 It is necessary that medicines are tested on healthy people so that side effects are clear and distinguished from the symptoms of the disease being treated. If people are to give up time and possibly take risks they should be paid. However payment means that some people may volunteer for the wrong reasons. The two groups who most commonly volunteer are prisoners and students.

5 One approach is for the agencies that buy medicines, such as the NHS, to use their purchasing power by restrict their choice of drugs that have been tested under conditions that respect the rights of the participants in trials. Another approach is for international agencies linked to the United Nations to check up on drug trials by the big pharmaceutical companies. Investigative journalists can study the issue and alert the public and politicians to the issue through their reporting.

6 a) Pharmaceutical companies may have little commercial incentive to develop drugs for diseases that are more common in developing countries, where the economic situation does not allow a profitable return on medicines sold.

Generic drugs produced by developing countries under license from the drug companies risk these cheaper versions (illegally) being made available outside the country with the licence, reducing profits for the company.

b) Large charitable foundations can intervene and give grants to support the research into treatments for diseases that it would not be commercially viable for industrial companies to fund. Similarly government aid programmes could support research of this kind.

7 a) Similarities: the people affected have limited political influence; income from sales is not large enough to fund research; incentives are needed to fund the research.

b) Differences: the diseases in developing countries may affect a large number of people, but the lack of market is due to the countrys economics. Orphan drugs are for diseases which only affect a small minority of people. The lack of market is due to small numbers.

8 a) Clearly sub-standard or ineffective drugs do no good to the patient. With some infectious diseases they may help to increase the problem of drug-resistance. They are a threat to programmes designed to eradicate infectious diseases.

b) The drugs in question are likely to be widely used because they are cheap and indeed may be the only drugs available. Governments can help by negotiating with pharmaceutical companies to make available reliable drugs at affordable prices.

9 The genetic material in the cells of the cloned embryo comes from the body cell. The donated egg has all its genetic material removed before nuclear transfer takes place. The parent of the clone is therefore the donor of the body cell.

10 Parkinsons disease and diabetes are conditions which arise because specialized cells in the body have ceased to produce the chemicals needed for normal health. The hope is that it will be possible to use stem cells to replace the cells that have been damaged or destroyed.

11 If scientists can find what triggers stem cells to specialise into different tissues, it is possible that, in the future, adult tissue stem cells could be used for therapeutic cloning in place of embryonic stem cells.

12 While there are serious doubts about the possible effects of stem cells in the body, the risks are not balanced by the potential benefits unless the patient is suffering from a life-threatening disease.

13 Pharmaceutical companies are businesses that need to make money through selling drugs. Their brochures cannot contain misleading material, but they may emphasise positive features and data over the less positive. Articles in peer reviewed journals are more likely to be critical, to point out any flaws in methods used to collect data, or in interpretation of the data.

14 Some people would argue that use of embryos in research is wrong, no matter what the circumstances, on the basis that the embryo has rights.

A utilitarian might argue that using discarded embryos brings about less harm than creating embryos for the purpose of research. Whether either is morally acceptable is a matter of whether the total good coming from the research outbalances the harm to the embryos.

15 Research on nuclear transfer in humans could, in principle, lead to human reproductive cloning. An embryo created by nuclear transfer may have the potential to develop normally if implanted in a uterus. Some people argue that technology which is open to such abuse should not be licensed.

Other ethical issues include the informed consent of the egg and body cell donors, and any harm that may come to women who are treated to produce multiple eggs for donation.

16 A 14 day human embryo is not recognizably human, or even recognizably animal. It is just a tiny group of cells which is about the size of a typical printed bullet point.

17 Before 14 days there is no possibility of the embryo suffering by any definition. There is not even a rudimentary nervous system in place. This is also the time up to which twinning is possible, so up to 14 days it could be argued that the embryo is not necessarily an individual. (It would be ideal to use quotes from e.g. the Warnock report in this answer).

18 The issues here are mainly to do with informed consent; permission would need to be given for any type of future research, and to use the genetic line to create cell lines or embryos for research or therapies. As future types of research are unknown, people would be giving consent for unknown actions.

Review questions

19 Ethical questions relate to values, they ask questions about whether or not things should be allowed to happen, and weigh up the risks and benefits for individuals and society (Should it be done?). Science gathers data through observation and experiment and seeks explanatory theories to account for patterns in data. Scientific knowledge explores what is possible (Can it be done?). Scientific data can be used to provide information about risks and benefits which can inform ethical arguments but not provide the final answers to questions that are not scientific.

20 a) A doctor might not want to avoid telling a patient that they have a terminal illness such as cancer. Also a doctor might want to delay telling the mother of a baby that there are signs which suggest that there is something seriously wrong with the baby.

b) A doctor has to judge a situation, and decide how much information a patient will benefit from. In some cases, the truth about a patients condition may not be certain, and the way the truth is delivered often changes the way it is received. Some patients express the wish not to know the truth, and this is considered a right. Telling the truth to patients is part of respecting them and allowing them autonomy. Patients have a right to informed consent, and this must include disclosure of any information condition or treatment they are involved in. Studies have shown better recovery rates or pain relief in patients who were given information about their condition and treatment.It is difficult to imagine a situation where lying would be an ethical option, but if the truth may cause distress or harm, this has to be taken into account when considering timing, support and counselling of patients who have received bad news.

21 The egg involved in nuclear transfer has no nucleus, so none of the genetic material found in chromosomes. The resulting cell and future embryo only has nuclear genetic material from one parent. This material comes from a donor body cell, so the embryos genetic parent is the body cell donor.



Chapter 6 Reproductive choices


1 Otherwise the amount of genetic material in each body cell in each generation would double, since each generation starts with the fusion of two sex cells to form the fertilised egg (the first body cell) from which an individual develops.

2 There are several forms of gene responsible for CF. There is one normal form and several forms that are faulty. The child inherits one version of the gene from the mother and another form from the father. Only one of the two inherited forms of the gene need be normal for the child to avoid CF. A carrier has one normal form and one faulty form of the gene. A person who is healthy and not a carrier has two normal versions of the gene. In the family in question, one parent has two normal versions of the gene and so any child will have at least one normal form and so cannot be affected by CF.

3 One in 25 people, in a white population, carry the faulty gene. The chance that both parents will be carriers is 1 in 625. Only 1 in 4 children inherit two recessive versions of the gene and get CF. So that is 1 in 2500.

4 If the baby lives to old age there is a probability of 50% (i.e. 0.5, equals a half) that it will develop Huntingdon's disease. Babies themselves are never affected by Huntingdon's disease as it only develops in adulthood.

5 Many people prefer to enjoy the years of healthy life in ignorance of any inherited certainty that they will suffer from the disease in middle age. Once one family member knows their genetic status in relation to Huntingdons, this affects all their offspring whether a positive or negative result. This responsibility to future generations is what drives some people to discover whether or not they have the Huntingdons gene, but other people find the responsibility of passing on the news to young children or teenagers difficult to bear.

6 a) If your relative who has heart disease is a woman this information predicts that your own risk of heart disease is nearly three times the average. If your relative with heart disease is a man then this indicates that your own risk is not quite as high at 2 to 2.5 times the average. (In either case your risk is higher if you are male than if you are female).

b) The effect is quite marked whether the relative with heart disease is male or female so it is unlikely to be directly sex-linked. More details of the exact pattern of inheritance would be required before reaching any conclusions.

7

tumour a growth or swelling formed from abnormal division of cells.

benign the growth may cause damage if it gets too large, but will not spread to other parts of the body.

malignant the tumour is capable of spreading to other parts of the body where further cancerous growths might occur.

8

Normal body cellCancerous cell

Processes in the cytoplasm Respiration and other processes happen as normalRespiration and other processes happen as normal

Extent of differentiationDifferentiated into skin, nerve, muscles and other cellsUndifferentiated

Genetic material in the nucleusThe DNA is largely as inherited. This may include genes that predispose individuals to particular cancersDNA largely the same as other cells but with a number of additional mutations

Cell divisionSome cells do not divide at all, others divide in a controlled way to replace cells lost by wear and injuryUncontrolled cell division gives rise to a growth of undifferentiated cancer cells.

Tendency to break away and spread to other parts of the bodyNo tendency to spread to parts of the body where they should not be foundTendency to spread and form further colonies of abnormal cells in other parts of the body.

9 a) The absence of error bars on the chart means that it is not possible to decide if the differences between the cancer rates for the various groups of people is statistically significant. However the much higher death rates between the native Americans on the one hand and the white and African American populations on the other does suggest that different ethnic groups differ in their tendency to develop breast cancer.

b) The observed differences in incidence and mortality of breast cancer between the different ethnic groups could be due to differences in many cultural and environmental factors including:

lifestyle including diet

socio-economic group

awareness and uptake of screening

attitudes to health and use of heath services.

All these factors could affect risk of breast cancer, and the different ethnic groups may have different degrees of tendency for one or more of these indirect risk factors.

10 a) If the human fetus has a right to life, it can be argued that those responsible for its welfare have a duty to ensure that it lives and lives well. This might mean that a pregnant woman has a duty not to smoke cigarettes, consume large amounts of alcohol or undertake other potentially harmful activities. Similarly, the woman, the father, medical practitioners and society in general can be argued to have a duty to ensure that the woman and her unborn baby receive enough food, have decent housing, access to medical care and so on.

b) This can arise if the growing fetus is, in someway, a threat to the health and wellbeing, or even survival, of the mother. In these circumstances the womens partner and family should be involved in the discussions as well as doctors.

The 1967 Abortion Act says that, subject to the agreement of two doctors, abortion is legal up to the 24th week if the continuance of the pregnancy would damage the physical or mental health of the pregnant woman or the continuance of the pregnancy would injure the physical or mental health of her existing family. Abortion is allowed after 24 weeks gestation if the pregnancy represents a risk to the woman's life, or grave, permanent injury to her health, or if there is substantial risk of serious fetal abnormality.11 A false positive is when a test gives the result 'positive' when, in reality, it should have given 'negative'. Similarly, a false negative is when a test gives the result 'negative' when, in reality, it should have given 'positive'.

12 a)Number of false positives is 9990.

b) Number of false negatives is 5. (In reality, it is impossible to have a false negative as high as 5% for a condition that only affects 0.1% of individuals.)

c) No absolute answer can be given. It depends on the severity of the condition and what happens to individuals identified as having the condition - for example, whether they are aborted (as happens with some genetic conditions) or given a special diet once they are born (as happens with some other genetic conditions).

d) A false negative means that the baby is not thought to be affected by the condition detected by the test. The baby is in fact affected and the consequence is that the baby or the mother misses out on necessary and appropriate treatments.

e) A false positive at the very least creates anxiety for the parents. More seriously the baby might be given a treatment that could be harmful. At worst the outcome is an unnecessary abortion that kills a healthy baby.

f) Again, the answer depends on the severity of the condition and the consequences of any treatments or actions that are based on the test.

13 Because no test is 100% reliable and it is best to consider the possibility that the result it gives may be false. Understanding the interpretation of test results is part of being able to give informed consent for the test.

14 Ethical issues might include:

Potential harm to the fetus through carrying out the test.

Attitudes to disability.

Rights of the mother versus rights of the fetus (if abortion is being considered).

Duty of care to the fetus as a result of the fetus rights on the part of the parents and family, medics and wider society.

Informed consent when agreeing to the tests which includes understanding the implications of positive and negative results, and the possibility of false positives and false negatives.

Ethical frameworks:

Utilitarian approaches migth advocate the reduction of genetic diseases in the population through screening and abortion.

Rights and duties could refer to the fetus, parents, mother alone or other members of society.

Autonomy would address issues of informed consent in relation to the tests.

Issues of justice would involve exploring whether all groups in society have similar access to information and services.

15 The chances of a carrier meeting a partner with the same faulty allele is rare, so youd only expect to see a recessive disease appearing in one generation.

16 Two cousins have married. The likelihood of close family members carrying the same recessive alleles means recessive conditions are likely to appear much more frequently where families inter-marry.

17 Gene therapy involving sex cells affects any offspring and the genetic changes will be carried over to the body cells of any descendants of the person treated. Gene therapy for body cells has the potential to relieve the symptoms of a sufferer, but the changes to DNA will not affect the next generation.

18 Although there are common ethical arguments both for and against gene therapy involving body cells and gene therapy involving body cells, there are ethical considerations that differ. In particular, gene therapy involving sex cells has consequences that are longer lasting and affect future individuals unable to give their consent to the treatment. Sex-cell gene therapy could make the way for designer babies, raising issues about the sort of qualities we value in human beings.

19 a) Individuals and families benefit from knowing more about their health risks so that they can make life-style changes or seek early diagnosis and treatment to make it less likely that they become seriously ill. In time there may be drugs designed to treat people with a specific genetic make-up.

b) Disadvantages for the family are a possible increase of anxiety, or even fear, especially if no treatment is available for the disease in question. Another disadvantage is that the information could be used by the health service to ration treatment to those more likely to benefit; also insurance companies might refuse to provide life insurance or raise the premiums for those with particular genetic predispositions. Some people might find themselves unemployable as a result of the results of genetic tests.

20 a) A potential benefit for society is that the total burden of health might be reduced and the resources of the health service might be used more effectively.

b) Equally greater knowledge on the part of individuals and families might substantially increase the demand for expensive treatments. Also there is significant cost to screening programmes. Screening increases the need for advice and counselling services to explain the results to people.

21 a) People act autonomously if they are able to make their own informed decisions and put them into effect.

b) A screening programme for the population most likely to be affected by the disease increase the autonomy of individuals by giving the information they need to decide whether or not to get married and then whether or not to have children. In the Jewish community in question individuals have the support of rabbis and other members of the community to help them come to terms with the results of genetic tests that show that they carriers. The tests are manageable and affordable because of the relatively small number of people involved.

22 There is no treatment for Huntingdon's disease. Screening is offered to individuals at risk.

23 Justice suggests that if a genetic test is available it should be available to all whatever their means. Testing the whole population with an expensive test would draw resources away from other aspects of the health service which can only be justified if the results of the tests can lead to comparable benefits. The money available for health care will never be enough to meet the growing demand and so difficult decisions have to be made. A possible issue with an expensive test is that it may be restricted to those who can afford to pay.

24 The 1 in 4 chance is the same for each child (like the 1 in 2 chance of getting heads when tossing a coin) the probability is averaged on large numbers of babies. So the answers are:

No

No

No

Yes

No

25 a) The answer to this depends on peoples opinion about the importance of trust in a relationship, and whether couples have a right to information that is available about their partner that may affect their offspring.

b) There are some jobs, such as being an airline pilot, for which is particularly important to recruit fit and healthy people. Excluding people from these jobs if they suffer from well-understood single-gene disorders could well be justified. The understanding of the genetics of multifactorial diseases will have to be much improved before less specific genetic indications could fairly be used to exclude people from jobs..

c) Mental illness is a disability in the same way as other physical conditions, and people should not be discriminated on such grounds. By law, there are some jobs where medical criteria for employment can be defined. This is very different from discrimination on the grounds of a risk of an illness. Long term scientific investigations are team efforts and it would be normal for the composition of the team to change during the life of the project. Here seems no justification for excluding someone who might have the potential to do excellent work for 20 years or more.

26 The test is virtually risk-free for the fetus and mother, so high risk individuals can be identified for consideration of the further tests. This reduces the number of pregnancies at r

as sis textbook answersav

Documents