A2.3 Viruses

Question 1

Which of the following describes structures that are found in all viruses?

Answer 1

genetic material and a capsid

Question 2

Give examples of viruses that have single-stranded RNA?

Answer 2

HIV, influenza, coronaviruses

Question 3

Some viruses contain a layer outside of their capsid, derived from the host cell membrane. This structure is called the ____________.

Answer 3

envelope

Question 4

True or false?

Viruses cannot infect bacteria.

Answer 4

False

Question 5

Some viruses are capable of switching between the lytic and lysogenic cycles when exposed to certain environmental conditions such as UV light or chemical mutagens.

Answer 5

Example: Lambda phage

Question 6

All viruses are individually capable of carrying out either the lytic cycle or the lysogenic cycle, but not both.

Answer 6

f (bacteriophage lambda infects e.coli bacteria)

Question 7

How does bacteriophage lambda gain access to the host cell?

Answer 7

The virus binds to receptors on the host cell membrane and inserts its genetic material directly into the cell.

Question 8

_____________ evolution is the process by which unrelated organisms independently evolve similar traits as a result of adapting to similar environments or selective pressures.

Answer 8

convergent

Question 9

Why do RNA viruses (retroviruses) have high rates of evolution?

Answer 9

They copy their genetic material using error-prone mechanisms such as reverse transcriptase enzymes and RNA polymerases.

Question 10

HIV is an example of a
______ which means it inserts a DNA copy of its RNA genome into host cells. HIV has a high
_____ rate which means it is able to evolve quickly.

Answer 10

retrovirus. mutation.

Question 11

The genome of adenoviruses is composed of ____, whilst the genome of retroviruses is composed of ____.

Answer 11

DNA, RNA

Question 12

The diversity of viruses suggests that they could have multiple origins, however viruses share several similar structural features, each with similar functions. What process could account for this?

Answer 12

convergent evolution

(independent evolution of similar features in organisms which are not connected by a common ancestor. )

Question 13

All viruses have _____ with protein coat (____)

Answer 13

genetic material (DNA or RNA), capsid (hexagon shape)

Question 14

HIV targets ______ cells which play an important role in the ____ system.

Answer 14

helper T cells, immune