Question 1

Which of the following best describes the process of horizontal gene transfer in bacteria?

Accepted Answer

Transfer of genetic material between cells of the same generation, often resulting in a recombinant cell.

Question 2

During DNA replication in bacteria, which enzyme is responsible for joining Okazaki fragments on the lagging strand?

Accepted Answer

DNA ligase

Question 3

A mutation changes the DNA sequence from $$	ext{TAC} to$$ $$	ext{TAG}. $$What type of mutation is this, and what is its likely effect on the protein?

Accepted Answer

Nonsense mutation; introduces a premature stop codon, resulting in a truncated protein.

Question 4

Which of the following statements about the central dogma of molecular biology is correct?

Accepted Answer

DNA is transcribed into mRNA, which is then translated into protein.

Question 5

Which of the following best explains why the genetic code is described as 'degenerate'?

Accepted Answer

Most amino acids are encoded by more than one codon.

Question 6

A bacterium is exposed to UV radiation, resulting in the formation of thymine dimers. Which repair mechanism is most likely to correct this damage?

Accepted Answer

Nucleotide excision repair

Question 7

In the lac operon of E. coli, what happens when lactose is present in the environment?

Accepted Answer

Allolactose binds to the repressor, preventing it from binding to the operator, and transcription occurs.

Question 8

Which of the following is a correct sequence of events during prokaryotic DNA replication?

Accepted Answer

Helicase unwinds DNA → RNA primer added → DNA polymerase synthesizes new strand → DNA ligase joins fragments

Question 9

Which of the following best describes the function of tRNA during translation?

Accepted Answer

Transports specific amino acids to the ribosome and matches its anticodon to the mRNA codon.

Question 10

A patient is treated with AZT, a nucleoside analog. What is the most likely effect of AZT on viral replication?

Accepted Answer

AZT is incorporated into viral DNA, causing incorrect base pairing and halting viral replication.

Question 11

Which of the following is true regarding the difference between prokaryotic and eukaryotic gene expression?

Accepted Answer

In eukaryotes, transcription occurs in the nucleus and translation in the cytoplasm.

Question 12

Which of the following is a likely consequence of a frameshift mutation in a gene?

Accepted Answer

All amino acids downstream from the mutation are changed, often severely disrupting protein function.

Question 13

Which of the following best describes the role of the operator in an operon?

Accepted Answer

It is the DNA segment that determines whether transcription will take place by binding the repressor.

Question 14

A bacterium acquires antibiotic resistance by taking up naked DNA from its environment. Which mechanism of horizontal gene transfer is this?

Accepted Answer

Transformation

Question 15

Which of the following statements about plasmids is correct?

Accepted Answer

Plasmids are self-replicating, circular DNA molecules that can carry antibiotic resistance genes.

Question 16

Which of the following is the correct base pairing in DNA, as shown in the key?

Accepted Answer

Adenine pairs with Thymine; Guanine pairs with Cytosine

Question 17

Which of the following best explains why Okazaki fragments are formed during DNA replication?

Accepted Answer

The lagging strand is synthesized discontinuously because DNA polymerase can only add nucleotides to the 3' end.

Question 18

A bacterium with an F factor plasmid transfers a copy of this plasmid to another bacterium via a sex pilus. What is the result of this process?

Accepted Answer

The recipient bacterium becomes F+ and can now initiate conjugation.

Question 19

Which of the following is a function of topoisomerase during DNA replication?

Accepted Answer

Relaxing supercoiled DNA ahead of the replication fork.

Microbial Genetics: DNA Structure, Replication, Transcription, Translation, Mutation, and Gene Transfer

Study Guide - Practice Questions