Question 1

Which enzyme is responsible for unzipping the DNA double helix during DNA replication in prokaryotes?

Accepted Answer

Helicase

Question 2

Why is the origin of replication in prokaryotic chromosomes typically AT-rich?

Accepted Answer

AT base pairs are less stable and require less energy to separate.

Question 3

During DNA replication, why must the lagging strand be synthesized in fragments (Okazaki fragments)?

Accepted Answer

Because DNA polymerase can only add nucleotides in the 5' to 3' direction.

Question 4

What is the function of DNA ligase during DNA replication?

Accepted Answer

It seals the gaps between Okazaki fragments on the lagging strand.

Question 5

Given the DNA template strand 5'-CGATCGGAT-3', what is the complementary strand produced during replication?

Accepted Answer

3'-GCTAGCCTA-5'

Question 6

Which of the following best describes the Central Dogma of molecular biology?

Accepted Answer

DNA → RNA → Protein

Question 7

What is the role of the sigma factor during transcription in prokaryotes?

Accepted Answer

It binds to the promoter region to help RNA polymerase initiate transcription.

Question 8

During translation, what is the function of tRNA?

Accepted Answer

It acts as a translator of the mRNA code into protein by bringing specific amino acids.

Question 9

Which of the following is the start codon in both prokaryotes and eukaryotes, and what amino acid does it code for in bacteria?

Accepted Answer

AUG; formyl-methionine

Question 10

Why is it beneficial for multiple codons to code for the same amino acid?

Accepted Answer

It reduces the impact of point mutations (silent mutations).

Question 11

Which of the following statements about prokaryotic gene expression is correct?

Accepted Answer

Transcription and translation can occur simultaneously.

Question 12

What type of operon is the lac operon, and how is it regulated?

Accepted Answer

Inducible; turned on by the presence of lactose

Question 13

A mutation that changes a codon for an amino acid into a stop codon is called:

Accepted Answer

Nonsense mutation

Question 14

Which of the following best describes conjugation in bacteria?

Accepted Answer

Transfer of DNA via direct cell-to-cell contact, often involving a pilus

Question 15

Which repair mechanism is responsible for removing and replacing mismatched bases that were not corrected during DNA replication?

Accepted Answer

Mismatch repair

Question 16

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

Accepted Answer

Insertion or deletion of one or more bases

Question 17

In the Ames test, what does a high number of revertant colonies indicate?

Accepted Answer

The chemical tested is likely mutagenic.

Question 18

Which of the following is a key difference between generalized and specialized transduction?

Accepted Answer

Generalized transduction can transfer any gene, while specialized transduction transfers only specific genes adjacent to the prophage.

Question 19

Which of the following equations correctly represents the semiconservative model of DNA replication?

Accepted Answer

$$	ext{Parental DNA} ightarrow 	ext{1 Parental Strand} + 	ext{1 New Strand}$$

Question 20

A bacterial cell is exposed to UV light, resulting in the formation of pyrimidine dimers. Which repair mechanism is most likely to fix this damage?

Accepted Answer

Photoreactivation (light repair)

Chapter 11: Microbial Genetics – DNA Replication, Gene Expression, Regulation, Mutations, and Recombination

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