01/05/23

Understanding Understanding OrganismsOrganisms

Revision powerpoint

(OCR Gateway)

01/05/23B1a – Fitness and HealthB1a – Fitness and Health

01/05/23Modern diets and health Modern diets and health problemsproblems

% obesity in the UK

01/05/23The Circulatory systemThe Circulatory systemThe circulatory system is responsible for pumping ______ around the body. We need blood to be taken around the body because blood contains ________ and _______. These are needed so that all the ____ in our bodies can produce _____ through _________.

Words – energy, blood, glucose, respiration, oxygen, cells

01/05/23Arteries and veinsArteries and veinsArteries carry high pressure blood away from the heart to the rest of the body. The blood is under pressure due to

heart contractions.

Veins carry low pressure blood back to the heart. They have thinner, less elastic walls

and have valves to prevent backflow of blood.

01/05/23Heart diseaseHeart disease

Cholesterol

01/05/23Heart disease and High Blood Heart disease and High Blood PressurePressure

Heart disease and high blood pressure are conditions where the ______ and blood vessels experience extra strain. They can be caused by:

• Excess weight• High stress levels• _____• Excess _______• Diets that are high in saturated ___, sugar or saltLong term high blood pressure can cause blood vessels to weaken or even ______. To DECREASE blood pressure regular exercise and a balanced ____ are a good start!

Words – alcohol, burst, smoking, heart, fat, diet

01/05/23Measuring Blood PressureMeasuring Blood PressureBlood pressure measurements are taken in terms of “Systolic pressure over diastolic pressure”.High blood pressure can cause heart attacks, strokes, dementia, heart disease and kidney disease.Low blood pressure can cause dizziness or fainting.

01/05/23Fitness and HealthFitness and Health“Having good health” means “being free from disease”

“Being fit” means “having an good ability to do physical activity” and can be measured in terms of stamina, strength, agility etc

01/05/23SmokingSmokingCigarettes contain 3 harmful things:1. NICOTINE, which is an ___________ drug that raises the

heart beat, narrows the arteries and so causes ____ _____ _____. This leads to heart _________.

2. TAR, which coats the lining of the _______ making them less able to take in oxygen. It also contains carcinogens which cause ______________.

3. CARBON MONOXIDE, which is a _______ ____ which joins up with ____ blood cells making them incapable of transporting _____________ around the body. In pregnant women it can cause oxygen deprivation, leading to low birth ______.Words – high blood pressure, oxygen, red, addictive,

disease, poisonous gas, lungs, cancer, mass

01/05/23Saturated Fat and Heart Saturated Fat and Heart DiseaseDisease

01/05/23B1b – Human Health and B1b – Human Health and DietDiet

01/05/23Balanced dietBalanced dietA balanced diet should contain fats, proteins and carbohydrates in roughly these amounts:

A good balanced diet should also contain water, vitamins, minerals and fibre.

• Carbohydrates are simple sugars such as glucose• Fats are made up of fatty acids and glycerol• Proteins are made up of amino acids

01/05/23Factors affecting choice of Factors affecting choice of dietdiet

What factors affectour choice of diet?

Age – teenagers need more

protein

Religion – some foods

may be banned

Activity – a sporty lifestyle will need more

energy

Personal choice, e.g.

vegetarianism

Allergies

01/05/23ProteinProteinProteins are long chains of amino acids.

Meat and fish are “first class” proteins

People who do not eat enough protein will not grow properly. Protein deficiency can result in a disease called kwashiorkor, where the muscles waste away and the belly swells. This is common in developing countries where overpopulation and limited investment in agriculture can cause food shortages. Proteins are used by the body as an energy source if fats are not present.How much protein should we eat?

EAR of protein (in g) = 0.6 x body mass (in kg)

There are two classes of protein: • Essential amino acids (must be eaten)• Non-essential amino acids (can be made in the body)

01/05/23Storing Food in our bodiesStoring Food in our bodiesHow do our bodies store food?

The liver converts glucose and other carbohydrates into

insoluble glycogen to be stored in the liver

Fats are stored under the skin and around organs as “adipose

tissue”

Proteins are not stored in the body.

01/05/23Body-Mass IndexBody-Mass IndexA commonly-used way to indicate is someone is overweight or underweight is the Body Mass Index (BMI):

BMI = Mass (kg)Height2 (m2)

BMI Meaning<18.5 Underweight

18.5-25 Ideal25-30 Overweight30-40 Obese – obesity is linked

to heart disease, diabetes and breast cancer

01/05/23Eating disordersEating disordersAnorexia nervosa – this is a condition where sufferers restrict what they eat and sometimes starve themselves, leading to possible weight loss, abdominal pains, discoloured skin, irregular periods etc.

Bulimia nervosa – this is when people vomit or take laxatives straight after eating to get the food out as quickly as possible. It can lead to weight fluctuations, poor skin, hair loss, irregular periods, tiredness etc.

01/05/23B1c – Staying HealthyB1c – Staying Healthy

01/05/23PathogensPathogensPathogens are microbes (micro organisms) that can cause diseases. They can enter the body in a number of ways:

…or other natural openings…

They can be breathed in through the mouth or nose

They can enter through cuts or bites in the skin

01/05/23Spreading of PathogensSpreading of PathogensDiseases and pathogens can be spread by a number of means, including:

Cholera bacteria, spread in water

Salmonella bacteria, found in food

Influenza virus, spread through the air

Athlete’s foot, a fungus spread through contact

Malaria, spread through “vectors”, e.g. mosquitoes

HIV, spread through body fluids

01/05/23Microbes: our defence against Microbes: our defence against themthemOur bodies have defence mechanisms against microbes:

If our skin is cut platelets seal the wound by clotting

The breathing organs have hairs and produce mucus to cover the lining of these organs and trap the microbes

The skin acts as a waterproof barrier

Our stomach contains hydrochloric acid

However, these mechanisms can’t do anything about non-infectious diseases (e.g. cancer) or inherited diseases (e.g. cystic fibrosis)

01/05/23What pathogens do to usWhat pathogens do to us

Pathogens can cause the damage or death of cells, e.g. in liver cirrhosis:

They can also damage the body by producing toxins:

01/05/23White blood cellsWhite blood cellsIf microbes enter our body they need to be neutralised or killed. This is done by WHITE BLOOD CELLS:

White blood cells do 3 things:1) They eat the microbe (these

white blood cells are called “phagocytes”)

2) They produce antibodies to neutralise the microbe (“lymphocytes”)

3) The produce antitoxins to neutralise the poisons produced by microbes (lymphocytes again)

01/05/23Producing antibodiesProducing antibodies

Step 1: The lymphocyte “sees” the pathogen (microbe)

Step 2: The cell produces antibodies to “fit” the antigen

Step 3: The antibodies fit onto the antigens and cause them to “clump”

Step 4: The pathogens are “eaten” by the white blood cells

You’re going down

01/05/23Specific antibodiesSpecific antibodies

Antibodies are specific for different antigens – they will only neutralise the microbe they have been made for.

01/05/23Fighting diseaseFighting diseaseNATURAL IMMUNITYThis is when antibodies are produced by a person when needed or they are passed on by the mother during pregnancy.

ARTIFICIAL IMMUNITYCan be done in two ways:1) A vaccine with dead microbes (which still

carry the antigen) is injected – the body is “tricked” into producing antibodies ready for the real thing. This is called PASSIVE IMMUNISATION and the body then “remembers” the microbe by producing memory cells that “remember” it

2) The antibodies are injected directly into the body – this is called ACTIVE IMMUNISATION.

01/05/23Vaccinations and Medicines Vaccinations and Medicines Vaccinations have eradicated some diseases entirely but they can carry some side effects.

Health problems can also be treated using antibiotics or antivirals:• Antibiotics are used to treat bacterial infections but they have to be used sparingly or the bacteria might become resistant (e.g. MRSA)• Antivirals are used to treat a virus, such as HIV.

01/05/23The importance of testing drugs – e.g. The importance of testing drugs – e.g. ThalidomideThalidomide

Mat Fraser, comedian and

actor

Tony Melendez, guitarist

01/05/23Developing new drugsDeveloping new drugsBefore a new drug can be approved it has to go through a strict testing process. Consider the example of thalidomide:Date Event

Mid 1950s

Late 1950s

Early 1960s

Mid 1960s

Animal testing using thalidomide was undertaken. Tests showed that it was safe but the tests were “inadequate” – no tests were done on pregnant animalsThalidomide prescribed to pregnant mothers to help sleep and morning sickness problems

Babies are born with birth defects and the drug was banned worldwide. Around 12,000 deformed Thalidomide babies born, 4,000 die in first year. Tests show that Thalidomide can help leprosy sufferers and it is still used today for this purpose.

01/05/2305/01/23Researching new medicinesResearching new medicinesBefore new drugs can be approved they have to go through three stages. What are the advantages and disadvantages of each stage?

3. Is it safe for humans? Human volunteers are tested on.

1. Is it toxic? Tests are done on cells

2. Is it safe for animals? Animal tests are carried out

01/05/2305/01/23PlacebosPlacebosClinical trials can be done in different ways:1) Blind trialsPatients do not know which drugs they are taking – a real drug or a “placebo”

2) Double blind trialNeither the doctors or the patients know if they are taking the real drug

Placebos offer anethical dilemma as a patient might be sick and still be given a “dummy” pill. Also, you might notice if you had a placebo as you wouldn’t get the side effects of normal drugs...

01/05/23MalariaMalariaParasite

Host

The spread of malaria can be restricted by:• Sleeping under mosquito nets• Taking malaria pills• Avoiding being bitten

01/05/23CancerCancerCancer is a disease where cells show uncontrolled growth.

Our diets can affect our chances of getting cancer:

“Good” foods:FruitVegetablesFibre

“Bad” foods:SaltSaturated fatsRed meat

Exercise can play a key part as well – Cancer Research UK recommends “30 minutes a day of moderate activity” 5 days a week, such as gardening, walking etc.

01/05/23TumoursTumoursTumours can be classed as “malignant” or “benign”:Malignant tumours are cancerous and will still growBenign tumours are not cancerous – they may still grow but won’t spread

This graph shows the survival rates of different types of cancer (source: Cancer Research UK). What conclusions can you draw from it?

01/05/23B1d – The Nervous SystemB1d – The Nervous System

01/05/23

Optic nerve

The EyeThe Eye

Retina

Pupil

Cornea

Ciliary musclesBlind spot

Optic nerve

Lens

Iris Sclera

01/05/23VisionVision

“Binocular vision” “Monocular vision”

What are the advantages and disadvantages of each?

01/05/23Seeing thingsSeeing things

Rays of light are refracted (bent) first by the cornea and then by the lens. They focus on the retina.

01/05/23Focussing on different distancesFocussing on different distancesFor distant objects the ciliary muscles

relax and the suspensory ligaments pull tight making the lens pull thin – the

light doesn’t bend as much.

For close objects the ciliary muscles

contract allowing the lens to go fat, thus bending the light

more.

01/05/23Problems with visionProblems with visionShort sighted Long

sighted

Colour blindness, caused by a lack of specialised cells in the cornea

01/05/23Using lenses to correct Using lenses to correct visionvision

Short Long

Laser eye surgery could also be used, which basically reshapes the cornea

01/05/23The Nervous SystemThe Nervous SystemThe CENTRAL NERVOUS SYSTEM (CNS) enables us to react to our surroundings. It consists mainly of the brain, the spinal chord, nerve cells (“neurones”) and receptors.

Types of receptor:1) Light receptors in the eyes2) Sound receptors in the ears3) Taste receptors on the tongue4) Smell receptors in the nose5) Touch, pressure and temperature receptors in the skin6) Changes of position receptors in the ears (balance)

01/05/23Nervous ReactionsNervous ReactionsWhen we react to a stimulus our bodies use the following pattern:

Stimulus Receptor Coordinator Effector ResponseFor example, consider

a man and a camel: Oh No!

What are the stimulus, receptor, coordinator, effector and response in this situation?

01/05/23Examples of reactionsExamples of reactionsStimulus Receptor

(i.e. the thing that detects the stimulus)

Effector (i.e. the thing that will do

the reaction)

Response (i.e. action

taken)

Bright light

Sour taste

Losing balance

Sit on a drawing pin

01/05/23Structure of a nerve cellStructure of a nerve cellNucleus Muscle strands

(effector)Cell body

1) Motor neurone 2) Sensory neurone 3) Relay neurone

Impulse Impulse

Axon

Myelin sheath – increases the speed of transmission

Dendrons – conduct the impulse to the cell

01/05/23SynapsesSynapses

Neurones never ____ each other – there is a small gap between them called a _____. A signal is sent from one _______ to the next by a _______ transmitter across the synapse. These transmitters are then ________.

Words – chemical, synapse, neurone, touch, destroyed

01/05/23Conscious actionsConscious actionsA conscious action is one where the brain makes a considered response. Here’s what happens:

Stimulus Receptor Sensory Neurone Coordinator Motor Neurone Effector Response

1) Receptors in your skin detect a stimulus

3) Here another sensory neurone carries the signal to the brain

4) The brain decides to move away the hand

5) This impulse is sent by MOTOR NEURONES to the hand muscles (the effectors) via the spinal chord…

2) The impulse is carried by SENSORY NEURONES to the spinal chord

6) Which then moves the hand away

01/05/23Reflex actionsReflex actionsSometimes conscious action is too slow to prevent harm, e.g…

In situations like this the body bypasses the brain to produce a quicker response. Here’s how it works…

01/05/23Reflex actionsReflex actions

1. Receptor

2. Sensory neurone

3. Relay neurone in the spinal chord

4. Motor neurone

5. Effector

Stimulus Receptor Sensory Neurone CNSMotor Neurone Effector Response

01/05/23B1e – Drugs and YouB1e – Drugs and You

01/05/2301/05/23Cannabis: Pros and consCannabis: Pros and consIn January 2004 cannabis was changed from a class B drug to a class C drug. Some people think that Cannabis should be made legal. What are the pros and cons of cannabis?Pros:

Cons:

01/05/2301/05/23Drugs Research ProjectDrugs Research ProjectExplain and give examples for the following:

1) Define the terms addiction, tolerance, withdrawal symptom and rehabilitation.

2) Why do people use legal drugs?

3) What are the drawbacks of legal drugs?

4) Alchohol is a legal drug. What does it do to the human body?

5) Why do people use illegal drugs?

6) What are the drawbacks of illegal drugs? What can they cause?

7) Choose one drug and discuss how it affects the human body

01/05/2301/05/23Legal drugsLegal drugsDrug Effect on

activitiesAbnormal

behaviour caused

Caffeine/ other stimulants

Alcohol

Paracetamol/ other painkillers

Reactions could become faster

Highly strung, leads to exhaustion

May make you drowsy, you shouldn’t drive

Leads to depressant effects on the nervous system

May make you drowsy, you shouldn’t drive

Side effects include dizziness or itchiness

Overall, the effect of these legal drugs can be greater than the effect of illegal drugs simply because more people use them.

01/05/23DrugsDrugsDrugs are classed as “a substance that affects the central nervous system, causing changes in psychological behaviour and possibly addiction”. Some examples:Type of drug Effects Examples

Painkiller Block nervous impulses

Morphine, aspirin, paracetamol

Hallucinogen Distort sense perception

LSD

Stimulant Increase reactions Caffeine, nicotine, ecstasy

Depressant Slow down brain activity

Alcohol, solvents, termazapam

01/05/23Synapses and drugsSynapses and drugs

Depressant drugs can bind with ______ molecules in the membrane of adjacent _______ and block the transmission of an ______.Stimulants can cause more ___________ to cross the ________.

Words – neurotransmitter, receptor, synapse, neurones, impulse

01/05/23Investigating Reaction Investigating Reaction TimesTimes

Task: Design an experiment that investigates the affect of caffeine on reaction times.Variables: What are the independent, dependant and control variables?

Results: Draw your own results table:

Conclusion: What do your results show you?

01/05/2301/05/23SteroidsSteroidsSteroids are drugs that are used to boost athletic performance. They’re banned and using them will lead to disqualification from competing.

This picture isn’t real…Ben Johnson, who ran the 100m in 9.79 seconds in 1988 but had his Olympic gold medal stripped away from him after testing positive for steroids.

01/05/23Smoking revisitedSmoking revisitedCigarettes contain 4 harmful things:1. NICOTINE, which is an ___________ drug that raises the heart beat,

narrows the arteries and so causes ____ _____ _____. This leads to heart _________.

2. TAR, which coats the lining of the _______ making them less able to take in oxygen. It also contains carcinogens which cause ______________.

3. CARBON MONOXIDE, which is a _______ ____ which joins up with ____ blood cells making them incapable of transporting _____________ around the body. In pregnant women it can cause oxygen deprivation, leading to low birth ______.

4. Particulates, which accumulate in the lungs.

Words – high blood pressure, oxygen, red, addictive, disease, poisonous gas, lungs, cancer, mass

01/05/23Diffusion in the lungsDiffusion in the lungsOxygen diffuses in and carbon dioxide diffuses out of blood in the lungs:

O2

CO2

01/05/23Damaging the lings Damaging the lings (emphysema)(emphysema)

Before smoking

After smoking –

less surface area

Another way smoking can damage the body is through destroying the shape of alveoli:

01/05/23More damage by smoking – smoker’s More damage by smoking – smoker’s coughcough

The “pink” hairs in this photo show cilia, small hairs lining the windpipe that clear dust and other particles away from the air we breathe. Regular smoking causes the cilia to become paralysed and excess mucous and tar build up in the lungs, causing smoker’s cough.

01/05/23Tobacco and Lung CancerTobacco and Lung Cancer

Sir Richard Doll, 1912-

2005

Over 50 years I proved the link between smoking and lung cancer. I published my first findings in 1950, based on patients in

London hospitals, and then studied 40,000 doctors and proved a link in a

paper published in 1954.

Smoking has existed in Western culture since the 16th Century. However, scientists only proved the link between it and various diseases shortly after the Second World War.

01/05/23Cancer Research UK Cancer Research UK statisticsstatistics

What do these statistics imply?

01/05/2301/05/23The Effects of AlcoholThe Effects of AlcoholTime Effects

Short term

Long term

Blurred vision, lowering of inhibitions, slowing of reactions (hence why there is a limit on drink-driving)Liver cirrhosis, brain damage

Alcohol content is measured in %ABV. Wine is typically 12% while beer is 4-6%. 40% of hospital A&E incidents are alcohol-related. When the liver removes alcohol it turns it into toxic chemicals that cause liver damage or liver cirrhosis:

01/05/23B1f – Staying in BalanceB1f – Staying in Balance

01/05/23HomeostasisHomeostasisHomeostasis means “controlling internal conditions”:

Waste products that need to be removed + howCO2

Internal conditions that need controlling + howTemperature

Water content

Produced by respiration, removed via lungs

Increased by shivering, lost by sweating

Increased and decreased by hormones

Some of these mechanisms are controlled by “negative feedback” systems, i.e. the absence of a particular hormone causes the reaction to change.

01/05/23Measuring Body Measuring Body TemperatureTemperature

Some possible methods…

Body thermometers/

probes

Heat sensitive strips

Thermal imaging

Common places to measure temperature are in the armpit, the mouth, the fingers, the ears or the anus.

01/05/23Controlling Body Controlling Body TemperatureTemperature

Wow it’s hot! My body temperature needs to stay at

37OC as its the best temperature for the enzymes in my body. How does my body keep the temperature right?

Also, temperature sensors in the skin detect the heat and send information to the brain.

The thermoregulatory centre in the brain detects “warm blood”.

When the brain detects the high temperature it takes two main steps....

01/05/23Maintaining Body Maintaining Body TemperatureTemperature

Cold Hot

Vasodilation

VasoconstrictionVasodilation increases heat transfer to the surroundings and heat is also lost through the evaporation of sweat.

01/05/23Heat stroke and Heat stroke and hypothermiahypothermia

01/05/23Body Temperature and the Nervous Body Temperature and the Nervous SystemSystem

Effectors (muscles and sweat glands) carry out the response

Nerve endings in the skin detect the external temperature

Temperature detectors in the brain detect the blood

temperature

The hypothalamus coordinates a response using hormones

01/05/23Controlling Blood Sugar Controlling Blood Sugar levelslevelsWe need glucose in our bodies to help our cells to respire

and produce energy. What happens if we have too much glucose?

If blood sugar is too high the pancreas releases insulin, which

travels in the blood stream. Insulin lowers blood glucose

levels by converting glucose into insoluble glycogen.

If glucose levels fall too low then the hormone glucagon

is released from the pancreas which causes liver to turn glycogen back into glucose. The trouble with hormones is that they are

slower than nervous reactions.

01/05/23DiabetesDiabetes

What is diabetes?What do the pens (above right) do?What does an insulin injection (above left) do?What is the difference between Type 1 and Type 2 Diabetes?How does physical activity affect Type 1 and Type 2 Diabetics?

01/05/23DiabetesDiabetesType 1 Diabetes is a ________ in which a person’s blood sugar (i.e. glucose) level may rise to a _______ level. This is because the ______ doesn’t produce enough _________. Physical activity will _______ the amount of glucose needed by the body.

Diabetes can be treated by __________ carefully or by injecting extra insulin when needed. Diabetics have to test their blood sugar level before they decide how much insulin to _______ themselves with. Type 2 Diabetes occurs when the patient becomes _______ to insulin so the patient will have to be careful regarding physical activity.

Words – insulin, disease, inject, dangerous, eating, pancreas, increase, resistant

01/05/23B1g – Controlling Plant B1g – Controlling Plant GrowthGrowth

01/05/23Plant Growth IntroductionPlant Growth IntroductionPlants grow due to their cells dividing through mitosis. The cells then specialise into root hair cells, palisade cells etc. Unlike animals, plants continue to grow for the rest of their lives.

01/05/23Plant HormonesPlant HormonesThe growth of roots and shoots is controlled by hormones called auxins that move through the plant in solution:

In the roots hormones slow down growth of the cells in the lower region, which makes the root bend down.

In the shoots the hormone auxin is “destroyed” by light, so the shoot will bend towards the light as the cells on the shaded side grow quickest.

01/05/23Some DefinitionsSome Definitions

Shoots grow towards light (positive phototropism) and against gravity (negative geotropism). This is caused by cell elongation on the underside of the shoot and this happens because auxin is made in the tip and is unevenly distributed through the shoot.

Roots grow away from light (negative phototropism) and in the direction of gravity (positive geotropism). This is caused by cell elongation on the upper side of the root.

01/05/23Artificial Plant HormonesArtificial Plant HormonesHormones can be used to help plant growth and the development of fruit:1) Auxin

This hormone helps fruit to develop

2) Ethene

This hormone helps fruit to ripen

Other uses include rooting powders (to help root development), control of dormancy and weedkilling.

01/05/23B1h – Variation and B1h – Variation and InheritanceInheritance

01/05/23VariationVariation“Variation” is the name given to differences between individuals of the SAME species.Variation is due to GENETIC or ENVIRONMENTAL causes. For example, consider dogs:

1) Ways in which they are the same:

2) Ways in which they are different:

01/05/23VariationVariationVariation means “differences within a species. For example, consider some of the people in your class:

Ways in which they are the same

Ways in which they are different

01/05/23Environmental differencesEnvironmental differencesSome of this variation is due to our parents, but some of it is due to our upbringing and the environment in which we live – this is called “Environmental variation”.

Variation due to inheritance only

Variation due to environment only

Variation due to a bit of both

01/05/23Genes, Chromosomes and Genes, Chromosomes and DNADNA

Humans have 23 pairs of chromosomes. Different species have different numbers of these pairs.

01/05/23Sexual ReproductionSexual Reproduction

The human egg and sperm cell (“GAMETES”) contain 23 chromosomes each.

When fertilisation happens the gametes fuse together to make a single cell called a ZYGOTE. The zygote has 46 chromosomes (23 pairs) and contains information from each parent.

We have similar characteristics to our parents due to genetic information being passed down in genes through gametes:

01/05/23Sexual vs. Asexual Sexual vs. Asexual reproductionreproduction

Sexual reproduction:•2 parents are needed•Offspring will have “pairs” of chromosomes•This will cause genetic variation

Asexual reproduction:•Only 1 parent needed•Offspring are GENETICALLY IDENTICAL to parent (“clones”) “Snuppy” – the

first cloned dog (Aug 05)

01/05/23Boy or Girl?Boy or Girl?

X Y X

XX XYGirl Boy

“Allele”

01/05/23

Father

Mother

Son

Daughter

Boy or Girl?Boy or Girl?

01/05/2301/05/23Key wordsKey wordsGenotype

Phenotype

Allele

Dominant

Recessive

Homozygous

Heterozygous

•This allele determines the development of a characteristic•The characteristic caused by the genotype•This allele will determine a characteristic only if there are no dominant ones•This word refers to a pair of chromosomes being made of two different alleles of a gene•The genetic make up in a nucleus•This word refers to a pair of chromosomes being made of two of the same alleles of a gene•An alternative form of a gene

01/05/23Eye colourEye colourIn eye colour the brown eye allele is dominant, so we call it B, and the blue eye is recessive, so we call it b:

bbBB Bb

Homozygous brown-eyed

parent

Heterozygous brown-eyed

parent

Blue-eyed parent

What would the offspring have?

01/05/23Eye colourEye colourExample 1: A homozygous brown-eyed parent and a

blue-eyed parent:

Example 2: 2 heterozygous brown-

eyed parents

BB bbX Bb BbXParents:

Gametes:

Offspring: Bb Bb BbBb BB Bb bbbB

B B bb B bB b

(FOIL)

All offspring have brown eyes

25% chance of blue eyes

01/05/23Eye colourEye colourExample 3: A heterozygous brown-eyed father and a blue-eyed mother:

Bb

Bb Bb bbbb

bb

b bB b

Equal (50%) chance of being either brown eyed or blue eyed.

01/05/23

B bbb

Another method – the “Punnett Another method – the “Punnett square”square”

Example 3: A heterozygous brown-eyed father and a blue-eyed mother:

B bb Bb bbb Bb bb

Father

Mother

01/05/23Example questionsExample questions1) In mice, white fur is dominant. What type of offspring would you expect from a cross between a heterozygous individual and one with grey fur? Explain your answer with a genetic diagram.

2) A homozygous long-tailed cat is crossed with a homozygous short-tailed cat and produces a litter of 9 long-tailed kittens. Show the probable offspring which would be produced if two of these kittens were mated and describe the characteristics of the offspring (hint: work out the kitten’s genotype first).

01/05/23Inherited diseasesInherited diseases1) Cystic fibrosis – a disease that causes thick and sticky mucus to coat the lungs, gut and pancreas, making breathing and digestion difficult. It’s caused by faulty recessive alleles:

2) Huntingdon's disease – a disease of the nervous system that causes shaking, memory loss, mood changes and eventually dementia. It’s caused by a faulty dominant allele:

3) Sickle cell anaemia – a disease that alters the shape of red blood cells, thereby reducing their oxygen capacity, causing weakness and anaemia. It’s caused by recessive alleles:

Ff FfX

Cc ccX

Ss SsX

01/05/23Family Pedigree ChartsFamily Pedigree Charts01/05/23

Consider the following chart of the offspring and grandchildren between two sickle-cell anaemia carriers:

Key:= male

= female

= S allele

= s allele

Q. Describe the genotype and the phenotype of each of the grandchildren. Also, which member of

this family has got sickle-cell anaemia?

01/05/23The debate over genesThe debate over genesThe “Nature vs Nurture” debate is all about whether or not certain attributes or abilities are down to genetic reasons or through upbringing, e.g.:

Intelligence

Sporting ability

Good health