IB Biology HL A2.3 Viruses Hl Only Questions

small/fixed size;

nucleic acid/DNA/RNA;

capsid (made from protein);

no cytoplasm;

few or no enzymes;

attachment protein;

Marking guidance:

Do not accept genetic material.

1 max

a. variation in size/shape

OR

helical versus spherical / spikes versus no spikes / other contrasting shapes;

b. head and tail in bacteriophage (lambda) and polyhedral/spherical in HIV/COVID-19;

c. DNA or RNA as genetic material;

d. retroviruses/HIV has reverse transcriptase (but other viruses do not);

e. DNA in bacteriophage lambda and RNA in HIV/COVID-19;

f. single-stranded or double stranded DNA/RNA/nucleic acid;

g. bacteriophage lambda with double stranded and HIV/COVID-19 with single stranded;

h. circular or linear DNA / linear DNA in bacteriophage lambda;

i. variation in number of DNA/RNA/nucleic acid molecules

OR

HIV/other virus example with more than one molecule (of DNA/RNA);

j. some viruses are enveloped (in plasma membrane from the host cell);

k. bacteriophage lambda is a naked virus and HIV/COVID-19 is enveloped;

I. rapid evolution due to short generation time/rapid mutation rate/no proofreading/intense natural selection;

m. changes in influenza coat proteins/coronavirus spike proteins;

Marking guidance:

Accept other verified and valid examples in marking points b, e, g, i, k and m.

Accept coronavirus instead of COVID-19.

Accept diagrams to show examples of structural differences for marking points b, e, g, i, k and m. Reject statements that some viruses have plasma membranes.

7
max

Similarities: [2 max]

a. in both lambda attaches to bacterial/host cell;

b. both insert DNA into the bacterial/host cell

OR

both infect the bacterial/host cell;

c. both use the bacterial/host cell (pathways) to replicate their DNA;

Differences [2 max]

d. in lytic (cycle), the viral DNA is replicated independently/remains separate from the bacterial/host DNA AND in lysogenic (cycle), the viral DNA integrates with the bacterial/host DNA;

e. in lytic viral/virion assembly occurs AND in lysogenic it is delayed/dormant;

f. in lytic, the bacterial/host cell is then destroyed/bursts/lysed AND in lysogenic it is delayed/not destroyed;

Marking guidance:

Do not accept answers referring to RNA, genome or genetic material instead of DNA. Use ECF for continued use of the above terms.

a. Do not accept that both cause cells to burst/die.

b. Do not accept insertion of virus into host cell.

c. Do not accept that the virus reproduces, it needs to be viral DNA replication.

Accept statements saying 'only' as implying that the other cycle is the opposite.

3
max