Question 1

Which of the following best explains why DNA replication is considered 'semi-conservative'?

Accepted Answer

Each new DNA molecule consists of one old strand and one new strand.

Question 2

A mutation changes a codon from UAU (tyrosine) to UAA. What type of mutation is this, and what is the likely effect on the protein?

Accepted Answer

Nonsense mutation; results in a shortened protein

Question 3

Which enzyme is responsible for relieving the twisting tension ahead of the replication fork during DNA replication?

Accepted Answer

Gyrase

Question 4

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

Accepted Answer

Nucleotide excision repair

Question 5

Which of the following statements about the lac operon is correct when both glucose and lactose are present in the environment?

Accepted Answer

The lac operon is expressed at low levels because cAMP is low and the repressor is inactive.

Question 6

Which of the following best describes the difference between prokaryotic and eukaryotic transcription?

Accepted Answer

Prokaryotic mRNA can encode multiple proteins from a single transcript, while eukaryotic mRNA typically encodes one protein per transcript.

Question 7

A patient is infected with a bacterial strain that has acquired resistance to multiple antibiotics. Which genetic elements are most likely responsible for the rapid spread of this resistance among bacteria?

Accepted Answer

R plasmids and transposons

Question 8

During translation, which type of RNA is responsible for bringing amino acids to the ribosome?

Accepted Answer

tRNA

Question 9

Which of the following scenarios best illustrates horizontal gene transfer?

Accepted Answer

A bacterium acquires a plasmid carrying an antibiotic resistance gene from another unrelated bacterium.

Question 10

Which of the following best describes the function of DNA ligase during DNA replication?

Accepted Answer

Joins Okazaki fragments on the lagging strand

Question 11

A scientist introduces a base analog into a bacterial culture. What is the most likely effect of this mutagen?

Accepted Answer

It mimics normal bases and causes mispairing during replication.

Question 12

Which of the following is true regarding the genetic code?

Accepted Answer

It is redundant, meaning multiple codons can code for the same amino acid.

Question 13

A bacterium is able to take up naked DNA from its environment and incorporate it into its genome. This process is known as:

Accepted Answer

Transformation

Question 14

Which of the following best explains why transcription and translation can occur simultaneously in prokaryotes but not in eukaryotes?

Accepted Answer

Eukaryotic DNA is located in the nucleus, so mRNA must be exported before translation.

Question 15

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

Accepted Answer

Insertion or deletion of one or two bases

Question 16

Which of the following is a key feature of an inducible operon such as the lac operon?

Accepted Answer

The repressor is normally active, and the presence of an inducer inactivates the repressor to turn genes ON.

Question 17

Which of the following best describes the role of plasmids in bacterial genetics?

Accepted Answer

They are small, circular DNA molecules that replicate independently and often carry accessory genes such as antibiotic resistance.

Question 18

A bacteriophage transfers a random fragment of bacterial DNA from one cell to another. This process is known as:

Accepted Answer

Generalized transduction

Question 19

Which of the following best explains how transposons contribute to the spread of antibiotic resistance among bacteria?

Accepted Answer

Transposons can carry resistance genes and insert them into plasmids, which can then be transferred between bacteria.

Question 20

A bacterial cell with an F plasmid integrated into its chromosome is called an Hfr cell. What is the significance of Hfr cells in gene transfer?

Accepted Answer

They can transfer chromosomal genes to recipient cells during conjugation.

Molecular Biology and Microbial Genetics: Study Guide

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