Question 1

Which of the following best describes the main difference between vertical and horizontal gene transfer in bacteria?

Accepted Answer

Vertical gene transfer is the transfer of genetic material from parent to offspring during reproduction, while horizontal gene transfer is the movement of genetic material between organisms that are not in a parent-offspring relationship.

Question 2

During bacterial transformation, what is the most likely source of the DNA that is taken up by a competent cell?

Accepted Answer

Free-floating DNA fragments in the environment, typically originating from lysed, closely related bacteria.

Question 3

Which DNA repair mechanism is primarily used by bacteria to incorporate exogenous DNA during transformation?

Accepted Answer

Homologous recombination

Question 4

In bacterial conjugation, what makes a cell competent to initiate DNA transfer to another cell?

Accepted Answer

Possession of the F plasmid, which encodes the machinery for pilus formation.

Question 5

Which of the following statements about transduction is correct?

Accepted Answer

Transduction involves the transfer of bacterial DNA via a bacteriophage.

Question 6

A bacteriophage is capable of generalized transduction. Which of the following best describes the DNA that can be packaged into its capsid?

Accepted Answer

Any random fragment of the host bacterial genome.

Question 7

Which of the following limits the maximum amount of bacterial DNA that can be transferred by transduction?

Accepted Answer

The capacity of the bacteriophage capsid.

Question 8

Which type of virus is most likely to be capable of specialized transduction, and why?

Accepted Answer

A lysogenic phage, because it integrates into a specific site in the host genome and can excise with adjacent bacterial DNA.

Question 9

Which of the following best explains why a negative-strand RNA virus must carry an RNA-dependent RNA polymerase in its capsid?

Accepted Answer

The host cell lacks the enzyme needed to transcribe negative-strand RNA into mRNA.

Question 10

Which of the following steps occurs first in the lytic cycle of a bacteriophage?

Accepted Answer

Attachment of the phage to the host cell surface

Question 11

During the eclipse period of a lytic viral infection, which of the following is true?

Accepted Answer

No infectious virions are detectable in the environment.

Question 12

Which of the following best describes antigenic shift in influenza viruses?

Accepted Answer

Reassortment of genome segments when a host is co-infected with two different influenza strains, resulting in a new combination of antigens.

Question 13

A patient is infected with two different strains of influenza virus, each with 8 RNA segments. What is the probability that a newly formed virion will contain exactly one copy of each segment, assuming random assortment and that only 1 in 400 virions are viable?

Accepted Answer

$$P = \frac{1}{400}$$

Question 14

Which of the following is a key reason why it is difficult to develop an effective long-term vaccine for influenza?

Accepted Answer

Antigenic drift and shift result in frequent changes to viral surface proteins.

Question 15

Which of the following statements about prions is correct?

Accepted Answer

Prions are misfolded proteins that can induce misfolding in normal proteins, and lack any nucleic acid component.

Question 16

Which of the following best defines an endosymbiont?

Accepted Answer

A microorganism that lives inside the cells of a host and cannot survive independently outside the host cell.

Question 17

Which of the following is an example of an opportunistic pathogen?

Accepted Answer

A normally harmless skin bacterium that causes infection when introduced into the bloodstream via a wound.

Question 18

Which of the following best describes the difference between a virion and a viroid?

Accepted Answer

A virion is a complete virus particle with nucleic acid and protein coat, while a viroid is a small, circular RNA molecule without a protein coat.

Question 19

Which of the following is a mutualistic symbiosis?

Accepted Answer

A gut microbe that synthesizes vitamins for its host while receiving nutrients in return.

Question 20

Which of the following enzymes is required for a retrovirus to establish infection in a host cell?

Accepted Answer

Reverse transcriptase

Microbial Genetics, Viral Life Cycles, and Microbe-Host Symbiosis: Study Notes

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