Question 1

Which of the following best describes the semiconservative model of DNA replication?

Accepted Answer

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

Question 2

During bacterial DNA replication, which enzyme is responsible for unwinding the DNA double helix at the replication fork?

Accepted Answer

Helicase

Question 3

What is the primary function of single-stranded binding proteins (SSBPs) during DNA replication?

Accepted Answer

They prevent the separated DNA strands from re-annealing.

Question 4

Which of the following statements about the lagging strand during DNA replication is correct?

Accepted Answer

It is synthesized discontinuously in short fragments called Okazaki fragments.

Question 5

In the process of transcription, what is the role of the promoter region?

Accepted Answer

It is the binding site for RNA polymerase to initiate transcription.

Question 6

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

Accepted Answer

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

Question 7

Which of the following codons is a stop codon in the genetic code?

Accepted Answer

$$\mathrm{UAA}$$

Question 8

What is the function of tRNA during translation?

Accepted Answer

It brings amino acids to the ribosome and matches them to the mRNA codon.

Question 9

Which of the following is true about the lac operon in E. coli?

Accepted Answer

It is induced (turned on) in the presence of lactose.

Question 10

In the trp operon, what happens when tryptophan is abundant in the cell?

Accepted Answer

Tryptophan acts as a corepressor, activating the repressor to block transcription.

Question 11

Which of the following mechanisms of horizontal gene transfer involves the uptake of naked DNA from the environment?

Accepted Answer

Transformation

Question 12

A bacterium receives a plasmid carrying antibiotic resistance genes through direct cell-to-cell contact. Which process is responsible?

Accepted Answer

Conjugation

Question 13

Which of the following statements about plasmids is correct?

Accepted Answer

They are self-replicating, extrachromosomal DNA molecules.

Question 14

In Griffith’s experiment with Streptococcus pneumoniae, what was the key finding?

Accepted Answer

Non-virulent bacteria became virulent when mixed with heat-killed virulent bacteria.

Question 15

Which of the following best describes the process of transduction?

Accepted Answer

Transfer of DNA by a bacteriophage from one bacterium to another.

Question 16

What is the role of DNA ligase during DNA replication?

Accepted Answer

It joins Okazaki fragments on the lagging strand.

Question 17

Which of the following is a feature of polycistronic mRNA in prokaryotes?

Accepted Answer

It codes for multiple polypeptides from a single mRNA transcript.

Question 18

A mutation in the operator region of the lac operon prevents the repressor from binding. What is the likely outcome?

Accepted Answer

The operon will be constitutively expressed, even in the absence of lactose.

Question 19

Which of the following best explains why Hfr cells can transfer chromosomal genes at high frequency during conjugation?

Accepted Answer

They have the F factor integrated into their chromosome, allowing transfer of adjacent genes.

Question 20

Which of the following equations correctly represents the directionality of DNA synthesis by DNA polymerase III?

Accepted Answer

$$5' \rightarrow 3'$$

Microbial Genetics: DNA Replication, Gene Expression, and Horizontal Gene Transfer

Study Guide - Practice Questions