Q: Which equation correctly estimates the number of genes in a bacterial genome, given its size in base pairs?

$\text{Number of genes} = \frac{\text{Genome size in base pairs}}{1000}$

Question 1

Which of the following statements best explains why plant genomes tend to be much larger than viral genomes?

Accepted Answer

Plant genomes contain more repetitive DNA and non-coding regions, while viral genomes are streamlined for rapid replication.

Question 2

A newly discovered bacteriophage has a genome size of 0.6 Mbp. Based on the provided materials, which of the following is most likely true about this phage?

Accepted Answer

It has one of the smallest genome sizes among cellular organisms.

Question 3

Which equation correctly estimates the number of genes in a bacterial genome, given its size in base pairs?

Accepted Answer

$	ext{Number of genes} = \frac{	ext{Genome size in base pairs}}{1000}$

Question 4

Which of the following best describes a pathogenicity island?

Accepted Answer

A region of DNA acquired through horizontal gene transfer that encodes virulence factors.

Question 5

If a strain of E. coli acquires a new toxin gene via horizontal gene transfer, which part of its genome is most likely to be affected?

Accepted Answer

The pan genome, increasing its diversity and pathogenic potential.

Question 6

Which of the following is a key difference between a lytic and lysogenic bacteriophage life cycle?

Accepted Answer

Lytic phages immediately replicate and lyse the host cell, while lysogenic phages integrate their DNA into the host genome and can remain dormant.

Question 7

During generalized transduction, what is the most likely genetic outcome for the recipient bacterial cell?

Accepted Answer

It may acquire random fragments of donor bacterial DNA packaged by a phage.

Question 8

Which enzyme is responsible for integrating phage DNA into the bacterial chromosome during lysogeny?

Accepted Answer

Integrase ($	ext{Int}$)

Question 9

A virus with a segmented RNA genome infects a cell already infected by a different strain of the same virus. What is the most likely consequence?

Accepted Answer

Antigenic shift, resulting in a new viral strain with mixed genome segments.

Question 10

Which of the following best describes the role of the spike protein in SARS-CoV-2 infection?

Accepted Answer

It mediates binding to host cell receptors and is the primary target for neutralizing antibodies.

Question 11

Which of the following is a correct statement about the Baltimore Classification Scheme for viruses?

Accepted Answer

It categorizes viruses based on their genome type and replication strategy.

Question 12

Which formula correctly represents the Central Dogma of molecular biology as it applies to most viruses?

Accepted Answer

$	ext{DNA} ightarrow 	ext{RNA} ightarrow 	ext{Protein}$

Question 13

Which of the following is a plausible reason why Mycoplasma genitalium has a very small genome?

Accepted Answer

It is an obligate pathogen that relies on its host for many essential functions.

Question 14

Which of the following best explains why Pseudomonas aeruginosa has a large genome compared to other bacteria?

Accepted Answer

It needs to adapt to diverse environments and encodes many metabolic and regulatory genes.

Question 15

Which of the following is a correct description of a viroid?

Accepted Answer

An infectious RNA molecule that lacks a protein coat and infects plants.

Question 16

Which of the following is true about prions?

Accepted Answer

They are misfolded proteins that induce abnormal folding in normal proteins, leading to neurodegenerative diseases.

Question 17

A scientist uses a plaque assay to quantify a virus. What is being measured in this experiment?

Accepted Answer

The number of infectious viral particles capable of lysing host cells.

Question 18

Which of the following best describes the function of restriction endonucleases in bacteria?

Accepted Answer

They protect bacteria by cutting foreign DNA, such as phage DNA.

Question 19

Which of the following is a correct statement about the mRNA COVID-19 vaccines?

Accepted Answer

They deliver mRNA encoding the SARS-CoV-2 spike protein, prompting host cells to produce the protein and stimulate an immune response.

Test 3 (Lecture 1) Genomes & Virology: Structure, Diversity, and Sequencing in Microbiology

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