Question 1

Which of the following best describes the difference between a bacterial chromosome and a plasmid?

Accepted Answer

A chromosome contains essential genes for survival, while a plasmid carries accessory genes that provide advantages such as antibiotic resistance.

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 a single base in a gene, resulting in a premature stop codon. What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 4

Which of the following statements about the lac operon is correct?

Accepted Answer

Allolactose acts as an inducer by binding to the repressor, inactivating it and allowing transcription of the lac genes.

Question 5

Which of the following best explains why DNA replication is described as 'semiconservative'?

Accepted Answer

Each daughter DNA molecule contains one parental strand and one newly synthesized strand.

Question 6

A bacterial cell is exposed to ultraviolet (UV) light, resulting in the formation of thymine dimers. Which DNA repair sequence is correct for fixing this damage?

Accepted Answer

Repair enzymes recognize the damage, remove the damaged DNA, DNA Polymerase fills the gap, and DNA Ligase seals the strand.

Question 7

Which of the following is true regarding the directionality of DNA and RNA synthesis?

Accepted Answer

Both DNA and RNA are synthesized in the $$5' \rightarrow 3'$$ direction.

Question 8

In the trp operon, what role does tryptophan play when present in high concentrations?

Accepted Answer

Tryptophan acts as a corepressor, activating the repressor to bind the operator and stop transcription.

Question 9

Which of the following best describes the function of the p53 gene in eukaryotic cells?

Accepted Answer

It acts as a surveillance gene, detecting DNA damage and helping maintain genome integrity.

Question 10

A scientist is using the Ames test to evaluate a new agricultural chemical. Which result would indicate that the chemical is a mutagen?

Accepted Answer

Histidine-dependent Salmonella grow on a plate lacking histidine after exposure to the chemical.

Question 11

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

Accepted Answer

In prokaryotes, transcription and translation can occur simultaneously in the cytoplasm.

Question 12

Which of the following is a consequence of a frameshift mutation?

Accepted Answer

Every codon after the mutation is changed, often resulting in a nonfunctional protein.

Question 13

Which of the following best describes the function of ribozymes in eukaryotic cells?

Accepted Answer

They are RNA molecules that act as enzymes to remove introns from pre-mRNA.

Question 14

A bacterial cell is growing in a medium containing both glucose and lactose. Which of the following best explains why there is a lag phase before lactose is metabolized?

Accepted Answer

The cell must synthesize the enzymes needed to metabolize lactose after glucose is depleted.

Question 15

Which of the following is the correct sequence of events during transcription in bacteria?

Accepted Answer

RNA polymerase binds the promoter, DNA unwinds, RNA is synthesized in the $$5' \rightarrow 3'$$ direction, terminator is reached, RNA is released.

Question 16

Which of the following best defines an operon?

Accepted Answer

A unit of DNA consisting of a control region (promoter and operator) and structural genes regulated together.

Question 17

Which of the following is true about the genetic code during translation?

Accepted Answer

Each codon on mRNA specifies a particular amino acid, and tRNA carries the corresponding anticodon.

Question 18

Which of the following is a correct comparison between positive (direct) and negative (indirect) selection in mutation detection?

Accepted Answer

Positive selection identifies mutants that grow or appear different, while negative selection identifies mutants that do not grow under certain conditions.

Question 19

Which of the following statements about DNA structure is correct?

Accepted Answer

The two strands of DNA are antiparallel, with one running $$5' \rightarrow 3'$$ and the other $$3' \rightarrow 5'$$, and are held together by complementary base pairing.

Microbial Genetics: DNA Replication, Gene Expression, Regulation, and Mutation

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