Question 1

Which of the following best describes the difference between genotype and phenotype in a bacterial cell?

Accepted Answer

Genotype is the genetic makeup of the organism, while phenotype is the observable characteristics resulting from gene expression.

Question 2

During DNA replication in bacteria, which enzyme is primarily responsible for synthesizing the new DNA strand by adding nucleotides to the growing chain?

Accepted Answer

DNA polymerase

Question 3

A scientist exposes a bacterial culture to ultraviolet (UV) light, which causes the formation of thymine dimers in DNA. Which DNA repair mechanism is most likely to be activated to correct this damage?

Accepted Answer

Photoreactivation (light repair)

Question 4

Which of the following statements about the genetic code is correct?

Accepted Answer

The genetic code is degenerate, meaning that most amino acids are encoded by more than one codon.

Question 5

In the lac operon of E. coli, what is the role of the repressor protein?

Accepted Answer

It binds to the operator to prevent transcription of the structural genes in the absence of lactose.

Question 6

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

Accepted Answer

Transfer of genetic material between unrelated bacteria, often via plasmids, transduction, or transformation.

Question 7

A point mutation changes a codon from $$	ext{UAC} ($$tyrosine) to $$	ext{UAA} ($$stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 8

Which of the following is a key difference between protein synthesis in prokaryotes and eukaryotes?

Accepted Answer

In eukaryotes, mRNA is processed by capping, polyadenylation, and splicing before translation.

Question 9

A researcher uses the Ames test to evaluate a chemical's mutagenicity. What is the primary indicator of a positive result in this test?

Accepted Answer

An increase in the number of revertant colonies compared to the control.

Question 10

Which of the following best describes the function of plasmids in bacteria?

Accepted Answer

They are small, circular DNA molecules that often carry genes for antibiotic resistance or other advantageous traits.

Question 11

A bacterial cell acquires a gene for antibiotic resistance via a bacteriophage. Which mechanism of genetic recombination does this represent?

Accepted Answer

Transduction

Question 12

Which of the following is an example of pre-transcriptional regulation of gene expression in bacteria?

Accepted Answer

Binding of repressors or activators to the operator region of DNA

Question 13

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

Accepted Answer

Insertion or deletion of one or more nucleotides not in multiples of three

Question 14

Which of the following statements about transposons is correct?

Accepted Answer

Transposons are segments of DNA that can move from one location to another within a genome.

Question 15

Which of the following best explains how genetic mutation and recombination contribute to natural selection in bacterial populations?

Accepted Answer

They provide new genetic variations that may confer a survival advantage under selective pressures.

Question 16

A scientist is trying to isolate a bacterial mutant that is resistant to a specific antibiotic. Which method would be most appropriate for directly selecting this mutant?

Accepted Answer

Plating bacteria on media containing the antibiotic and selecting for growth

Question 17

Which of the following equations correctly represents the semi-conservative model of DNA replication?

Accepted Answer

$$	ext{Parent DNA} ightarrow 	ext{1 old strand} + 	ext{1 new strand}$$

Question 18

Which of the following is a post-transcriptional regulatory mechanism in eukaryotes but not in prokaryotes?

Accepted Answer

Alternative splicing of pre-mRNA

Question 19

A bacterial cell is exposed to a chemical mutagen that increases the mutation rate from $$1 	imes 10$$^{-7}$$ to 1$$ 	imes $$10^{-5}$$ per gene per generation. What is the fold increase in mutation rate?

Accepted Answer

$$1000-$$fold

Question 20

Which of the following best describes the process of translation in protein synthesis?

Accepted Answer

Assembly of amino acids into a polypeptide chain based on the sequence of codons in mRNA

Microbiology Chapter 8: Genetics and Gene Expression Study Guide

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