Question 1

Which of the following best describes the process of generalized transduction in bacteria?

Accepted Answer

A bacteriophage transfers random fragments of bacterial DNA from one cell to another during the lytic cycle.

Question 2

A bacterial strain is unable to grow on minimal medium but grows on medium supplemented with tryptophan. What is the most likely explanation for this phenotype?

Accepted Answer

The strain is an auxotroph for tryptophan due to a mutation in the tryptophan biosynthetic pathway.

Question 3

Which of the following mutations is most likely to result from the incorporation of 5-bromouracil during DNA replication?

Accepted Answer

A transition mutation where an AT base pair is replaced by a GC base pair.

Question 4

A missense mutation in a gene results in which of the following outcomes?

Accepted Answer

A single amino acid change in the encoded protein.

Question 5

Which of the following best explains why RNA viruses have higher mutation rates than DNA viruses?

Accepted Answer

RNA viruses lack proofreading and repair mechanisms during replication.

Question 6

A bacterial cell is exposed to UV light, resulting in the formation of pyrimidine dimers. What is the most likely consequence if these dimers are not repaired?

Accepted Answer

The cell may experience mutations due to errors during DNA replication.

Question 7

Which of the following is a key feature of specialized transduction?

Accepted Answer

Only specific bacterial genes adjacent to the prophage integration site are transferred.

Question 8

A frameshift mutation is most likely to result from which of the following events?

Accepted Answer

Insertion or deletion of a single base pair in the coding region of a gene.

Question 9

Which of the following best describes the function of the RecA protein in bacterial transformation?

Accepted Answer

It mediates homologous recombination between donor and recipient DNA.

Question 10

A bacterial cell with a nonfunctional flagellum is most likely to display which phenotype on a motility agar plate?

Accepted Answer

Compact, non-spreading colonies.

Question 11

Which of the following is the correct sequence of events during bacterial conjugation involving an F+ and an F- cell?

Accepted Answer

Formation of a pilus, transfer of F plasmid DNA, synthesis of complementary DNA strand in recipient.

Question 12

Which of the following best explains the mechanism by which CRISPR-Cas systems protect bacteria from viral infection?

Accepted Answer

They recognize and cleave foreign DNA sequences using crRNA-guided Cas proteins.

Question 13

A bacterial strain is resistant to a particular antibiotic due to a mutation that alters the drug's target. Which class of mutant does this represent?

Accepted Answer

Drug-resistant mutant

Question 14

Which of the following is a likely outcome of treating bacteria with ethidium bromide?

Accepted Answer

Microinsertions and microdeletions due to intercalation between base pairs.

Question 15

A nonsense mutation can be suppressed by a second mutation in which of the following?

Accepted Answer

A tRNA gene that allows the tRNA to recognize the stop codon and insert an amino acid.

Question 16

Which of the following best describes the difference between conservative and replicative transposition?

Accepted Answer

Conservative transposition excises the transposon from the donor DNA, while replicative transposition leaves a copy in the donor.

Question 17

Which of the following is the most likely result of a single base substitution at the third position of a codon?

Accepted Answer

A silent mutation with no change in the amino acid sequence.

Question 18

A bacterial cell is exposed to nitrous acid, which deaminates adenine and cytosine. What type of mutation is most likely to occur?

Accepted Answer

Transition mutations such as $$\mathrm{A:T} \rightarrow \mathrm{G:C}$$ and $$\mathrm{G:C} \rightarrow \mathrm{A:T}$$

Question 19

Which of the following best describes the process of natural transformation in bacteria?

Accepted Answer

Uptake of free DNA from the environment and incorporation into the genome by homologous recombination.

Chapter Nine

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