Question 1

Which of the following statements best describes a plasmid in prokaryotes?

Accepted Answer

A small circular or linear DNA molecule that replicates independently of the host chromosome and often carries nonessential but helpful genes.

Question 2

Which feature distinguishes the core genome from the pan genome in microbial species?

Accepted Answer

The core genome is shared by all strains of a species, while the pan genome includes all genes found in any strain of that species.

Question 3

A researcher discovers a DNA segment in a bacterial genome with a GC content of $70\%$, while the rest of the genome averages $50\%$. What is the most likely explanation for this observation?

Accepted Answer

The segment was likely acquired through horizontal gene transfer.

Question 4

Which of the following is TRUE regarding R plasmids?

Accepted Answer

They confer resistance to antibiotics and other growth inhibitors.

Question 5

Which process is an example of horizontal gene transfer in bacteria?

Accepted Answer

Transfer of plasmid DNA from one cell to another via conjugation.

Question 6

A pathogenic bacterium is found to produce a toxin encoded by a gene located on a chromosomal island. What is the most likely origin of this gene?

Accepted Answer

It was acquired through horizontal gene transfer and is part of a pathogenicity island.

Question 7

Which of the following best describes metagenomics?

Accepted Answer

Analyzing pooled DNA or RNA from an environmental sample containing organisms that have not been isolated or identified.

Question 8

Why are plasmid-encoded bacteriocins important in microbial communities?

Accepted Answer

They help bacteria survive by inhibiting or killing closely related species or different strains of the same species.

Question 9

Which of the following is a function of plasmids in Rhizobia?

Accepted Answer

Encoding functions required for nitrogen fixation.

Question 10

A scientist is studying the human gut microbiome and finds a higher proportion of Firmicutes compared to Bacteroidetes. What health condition might this correlate with?

Accepted Answer

Increased obesity in humans and mice.

Question 11

Which of the following is NOT a characteristic of bacterial chromosomes?

Accepted Answer

They replicate independently of the cell cycle.

Question 12

Which of the following analyses would be most appropriate for studying the total protein content of a microbial community?

Accepted Answer

Metaproteomics

Question 13

A gene in a bacterial genome shows a codon usage pattern very different from the rest of the genome. What does this suggest?

Accepted Answer

The gene may have been acquired through horizontal gene transfer.

Question 14

Which of the following is a real-world application of genomics in microbiology?

Accepted Answer

Identifying drug targets for vaccine development.

Question 15

Which statement about chromosomal islands is correct?

Accepted Answer

They are acquired through horizontal gene transfer and often encode specialized functions.

Question 16

Which of the following best explains why plasmids are important in the evolution of bacterial populations?

Accepted Answer

They facilitate horizontal gene transfer, allowing bacteria to rapidly acquire new traits such as antibiotic resistance.

Question 17

A metagenomic study of a soil sample reveals DNA sequences from organisms that have never been cultured. What is the significance of this finding?

Accepted Answer

It shows that metagenomics can identify genetic material from uncultured and unknown organisms.

Question 18

Which of the following is a distinguishing feature of a pathogenicity island?

Accepted Answer

It encodes virulence factors that facilitate disease.

Question 19

If a bacterial strain contains a plasmid with a copy number of 50 per cell, what does this indicate about the plasmid?

Accepted Answer

It is a high-copy-number plasmid and may carry nonessential but helpful genes.

6, 10, 13: Genetic Elements in Microbes: Chromosomes, Plasmids, and Genomic Diversity

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