Viruses

Have you heard of…?

Avian Flu West Nile HIV SARS (severe acute respiratory syndrome) Chicken pox, measles, rabies, or polio common cold

All caused by viruses.

Discussion: Is a virus a living thing?

Evidence for living:

carry __________________ _________________________ _________________________

Characteristics of living things:

Made up of ___________

________________

________________________

________________________ (metabolism)

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________________________

Viruses are not considered living:

not ______________- only made up of genetic material and protein coat

do not ___________________________o if undisturbed, ________________________

do not do anything in nutrient agar (grow nor die) if undisturbed, __________________________ cannot _________________________ without a host cell Do not ________________________________ Cannot _____________________________

Tobacco Mosaic VirusHistoryIn the late 1800’s something was infecting tobacco plantations, causing bleached spots on the leaves forming a pattern the farmers called a mosaic. In 1892, Dmitri Ivanovsky investigated. He looked for infectious agents by crushing leaves of infected plants and passing juice of crushed plants through a filter small enough to ______

________________________.

He found the filtered juice from infected plants could still cause disease to another plant. Ivanovsky declared the disease was caused by a ______________________ too small to be seenwith the light microscope.

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Martinus Beijerinck called the filtered, infectious substance a "_______________" and this discovery is considered to be the beginning of ___________________-.

The name “virus” means __________________________- in Latin.

1931: Electron microscope allows for first imaging of viruses.

Transmission Electron Microscopy (TEM) is a technique in which a beam of electrons is transmitted through an ultra-thin specimen.

Although Louis Pasteur and Edward Jenner were the first to develop ____________________to protect against viral infections, they did not know that viruses existed.

Smallpox virus was a major cause of death in the 20th century, killing about 300 million people.Smallpox virus was a major cause of death in the 20th century, killing about 300 million people.Smallpox virus was a major cause of death in the 20th century, killing about _______________________.

Symptoms:

high fever. chills. malaise. headache.

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severe back pain. abdominal pain. vomiting.

Edward Jenner developed __________________:

Edward Jenner (1749–1823), a rural physician, contracted small pox as a boy. Jenner knew of a local belief that dairy workers who had contracted a relatively mild infection called cowpox were immune to smallpox. In 1796 he inoculated an 8 year old boy with Cow Pox.

Jenner then took some "_____________________" and repeatedly inoculated the boy who survived and was subsequently immune to smallpox.The word ___________________is derived from the Latin _______________meaning "cow".

Louis Pasteur developed Rabies Vaccination:

In France cures were desperately sought for rabies. Rabies is a viral disease that causes acute inflammation of the brain in warm-blooded animals. Pasteur (1822–1895) looked for the "_______________________" in mad dogs.

Pasteur showed that when the dried ________________________ from dogs that had died from rabies were crushed and injected into healthy dogs they did not become infected. He repeated the experiment several times on the same dog with tissue that had been dried for _______________________, until the dog survived even after injections of ________________________________.

Pasteur had immunised the dog against rabies.

Definitions

A virus is a __________________________________________________________________________________________________.

Acts _______________ by entering a host cell and using the material in the host cell to reproduce.

_______________ is the study of viruses and the diseases they cause. Bacteriophage is a virus that infects bacteria.

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Viron is the ____________________________________________________________ A ___________________is a bacteriophage (often shortened to "phage")

___________________inserted and integrated into the host bacterial DNA. ____________________ means that a virus can only attack particular cells

of a particular organism. Eg. Polio virus attacks nerve cellsMumps virus attacks salivary glands

____________________ is an RNA viruses that inserts a DNA copy of their genome into the host cell in order to replicate (e.g. HIV).

StructureViruses are ___________________-they lack most of the components of cells, such as organelles, ribosomes, and a plasma membrane.All viruses consist of:

a nucleic acid core (consisting of either RNA or DNA),

an _____________________ or ____________________ that encases the nucleic acid,

sometimes an ____________________ of lipid (fat) and protein molecules that is used to enter host cell (host lipid membrane cannot detect viral lipid membrane)

TEM image of a group of typical head and tail bacteriophage.

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Shape

Viruses come in many shapes and sizes, but these are __________________ and ____________________ for ______________________. In general, the shapes of viruses are classified into four groups:

Filamentous Isometrical Enveloped Complex

(Helical) (Polyhedral) (Spherical) (Head and Tail)

Filamentous viruses

are long and ______________________. Many plant viruses are filamentous, including TMV (tobacco mosaic virus).

Isometric viruses

have shapes that are roughly ___________________, poliovirus or herpesviruses.

Enveloped viruses

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____________________________________________________________. Animal viruses, such as HIV, are frequently enveloped.

Complex Head and tail viruses

infect _________________________. They have a head that is similar to icosahedral viruses and a tail shape like filamentous

viruses.

Size viruses can be up to ______________ than bacteria. 17-1000 nanometers

(1000nm = 1 micrometer) http://www.cellsalive.com/howbig_js.htm

Replication

Viruses exist in ______________________ When not in contact with a host cell, the virus remains

_______________________. o During this time the virus is static - no internal

biological activities occurring within the virus, o _____________ can remain in this dormant

state for extended periods of time, until they come into contact with the appropriate host, at which time it becomes ____________________ and is then referred to as a _________________. It now displays properties typified by living organisms, such as ________________ _________________ and directing its efforts toward _____________________.

http://highered.mheducation.com/sites/0072995246/student_view0/chapter8/lambda_phage_replication_cycle.html

LYTIC CYCLE Used by most viruses Produces symptoms immediately

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1. Attachment: - to host cell (All viruses have some type of protein on the outside coat that "recognizes" the proper host cell.) 2. Penetration: - genetic material _______________________________

- or host cell engulfs virus by process called __________________________- genetic instructions released into the host cell, - the injected genetic material ____________________ to the host cell's enzymes

3. Replication and protein synthesis:- host is directed to make __________________________ and protein-host cellular ____________________ make parts for more new virus particles

4. Assembly: - of _________________________________

- the new particles assemble into ______________________. 5. Release: - the new viral particles (virions) rupture the cell

- process called ____________________________. - The new virus particles leave the host cell, ready to infect other cells

LYSOGENIC CYCLE Produces symptoms some time after Host cell not lysed right away

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Steps 1 & 23b. Viral genetic material inserts into DNA of host cell

- call a ______________________- host DNA continues to function- may remain in host DNA for ________________________

4b. as host cell replicates, viral genetic material is also copied to the new cells of the host- viral genetic material remains ________________________________

- ___________________________________- ___________________________________

- activates to direct synthesis of new virions via the Lytic Cycle steps 3-5

ClassificationViruses are generally classified according to their:

________________________

________________________ ________________________

________________________ ________________________

1962: Linnaean hierarchical system Order (-virales) Family (-viridae) Subfamily (-virinae)

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Genus (-virus) Species (-virus)

Species names generally take the form of [Disease] virus.Eg Small pox Variola major and Variola minor

2013: Baltimore Classification system: seven groups depending their nucleic acid

No viral genome encodes a complete system for translating proteins; therefore all viral protein synthesis is completely dependent upon the translational machinery of the cell. David Baltimore created his virus classification scheme based on the the importance of viral genome in programming viral protein synthesis.

Role of Viruses in Ecosystem

Viruses are immensely important to the turnover of biomass in many ecosystems.

A teaspoon of seawater contains about one million viruses.

Microorganisms constitute more than 90% of the biomass in the sea. It is estimated that viruses kill approximately 20% of this biomass each day, and that there are 15 times as many viruses in the

oceans as there are bacteria. Viruses are the main agents responsible for the rapid destruction of harmful algal blooms, which often kill other marine life.

https://youtu.be/1PLBmUVYYeg

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http://sploid.gizmodo.com/clever-animation-explains-how-viruses-attack-our-cells-1564551563?utm_campaign=socialflow_gizmodo_facebook&utm_source=gizmodo_facebook&utm_medium=socialflow

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