Question 1

Which of the following best describes the difference between rolling circle replication and bidirectional replication in plasmids?

Accepted Answer

Rolling circle replication generates a single-stranded DNA intermediate that is later converted to double-stranded DNA, whereas bidirectional replication uses two replication forks to synthesize DNA simultaneously in both directions from the origin.

Question 2

A bacterial cell is exposed to a mutagen and then tested using the Ames test. Which result would indicate that the chemical is a mutagen?

Accepted Answer

The number of revertant colonies on the test plate is significantly higher than on the control plate.

Question 3

Which of the following sequences is most likely to be found at the -10 region of a bacterial promoter?

Accepted Answer

$$	ext{TATAAT}$$

Question 4

Which of the following best explains why Dr. Lederberg’s mixed mutant strains were able to grow on minimal media plates, while the individual mutants could not?

Accepted Answer

The mixed mutants underwent conjugation, allowing gene transfer between cells to complement each other's mutations.

Question 5

Which of the following is a function of the RecA protein in bacterial transformation?

Accepted Answer

RecA facilitates homologous recombination between incoming DNA and the host chromosome.

Question 6

A researcher wants to experimentally verify that DNA transfer has occurred between Hfr and F- cells. Which method would provide the most direct evidence?

Accepted Answer

Detecting the presence of donor-specific genetic markers in the recipient F- cells using PCR.

Question 7

Which of the following best describes the mechanism of Rho-independent termination of transcription in bacteria?

Accepted Answer

A stem-loop structure forms in the mRNA followed by a string of uracils, causing RNA polymerase to pause and dissociate.

Question 8

Which of the following statements about the F plasmid is correct?

Accepted Answer

The tra operon encodes the proteins necessary for pilus formation.

Question 9

Which of the following best describes the difference between generalized and specialized transduction?

Accepted Answer

Generalized transduction can transfer any gene from the donor, while specialized transduction transfers only genes adjacent to the prophage integration site.

Question 10

Which of the following best defines a riboswitch?

Accepted Answer

A segment of mRNA that changes its structure upon ligand binding to regulate gene expression.

Question 11

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

Accepted Answer

Nonsense mutation

Question 12

Which of the following is a key feature of the lac operon regulation in E. coli?

Accepted Answer

The lac repressor binds to the operator in the absence of lactose, preventing transcription.

Question 13

Which of the following best describes the function of the two-component signal transduction system in bacteria?

Accepted Answer

It allows bacteria to sense and respond to environmental changes via a sensor kinase and a response regulator.

Question 14

Which of the following statements about CRISPR defense mechanisms in bacteria is correct?

Accepted Answer

CRISPR systems incorporate short sequences from invading phages into the bacterial genome to provide adaptive immunity.

Question 15

Which of the following best describes the structure of a polysome?

Accepted Answer

Multiple ribosomes simultaneously translating the same mRNA molecule.

Question 16

Which of the following events occurs during the lysogenic cycle of phage lambda?

Accepted Answer

The phage DNA integrates into the host chromosome and is replicated along with the host genome.

Question 17

Which of the following is true regarding the influenza virus genome?

Accepted Answer

It consists of multiple segments of single-stranded RNA.

Question 18

Which of the following best describes the effect of ligand binding to methyl-accepting chemotaxis proteins (MCPs) in bacterial chemotaxis?

Accepted Answer

Ligand binding to MCPs decreases the frequency of clockwise flagellar rotation, causing the cell to run toward attractants.

Question 19

Which of the following statements about sRNAs and asRNAs is correct?

Accepted Answer

sRNAs regulate gene expression by base-pairing with mRNAs, while asRNAs are transcribed from the opposite strand of the target gene.

Question 20

Which of the following is a key difference between rolling circle replication in phage lambda and conventional rolling circle replication?

Accepted Answer

Phage lambda rolling circle replication produces linear concatemers with cos sites for packaging, while conventional rolling circle replication typically produces circular DNA molecules.

Microbiology Study Guide: Genetics, Gene Expression, Regulation, and Viral Genetics

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