Q: If a bacterial genome contains 20% cytosine (C), what is its GC content?

$$GC\ content = 2 \times 20\% = 40\%$$

Question 1

Which of the following statements 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 2

A double-stranded DNA sample from a bacterium is found to contain 18% guanine (G). What percentage of adenine (A) would you expect in this DNA?

Accepted Answer

$$A = 32\%$$

Question 3

During PCR, why must the two primers be oriented so that DNA synthesis proceeds toward the region being amplified?

Accepted Answer

Because DNA polymerase can only synthesize DNA in the $$5' \rightarrow 3'$$ direction, and both primers must direct synthesis toward each other to amplify the target region.

Question 4

Which of the following best describes the difference between the coding and template strands of DNA?

Accepted Answer

The coding strand has the same sequence as the RNA (except T is replaced by U), while the template strand is used by RNA polymerase to synthesize RNA.

Question 5

A researcher is analyzing a gene on a bacterial chromosome. For this gene, the top DNA strand is the coding strand. For a neighboring gene, the bottom strand is the coding strand. What does this illustrate?

Accepted Answer

The designation of coding and template strands is relative to each gene and not absolute for the entire DNA molecule.

Question 6

Which of the following is NOT typically found in a bacterial genome?

Accepted Answer

Telomeres

Question 7

Why is gene density much higher in bacterial genomes compared to human genomes?

Accepted Answer

Bacterial genomes have less noncoding DNA and fewer introns, resulting in more genes per megabase.

Question 8

Which of the following statements about genome organization is correct?

Accepted Answer

Eukaryotic chromosomes are linear and have telomeres, while bacterial chromosomes are usually circular.

Question 9

A student is designing a PCR experiment to amplify a specific gene. They select two primers that bind near the target region, but both are oriented in the same direction. What is the likely outcome?

Accepted Answer

No amplification will occur because DNA synthesis will not proceed toward each other across the target region.

Question 10

Which of the following best describes the role of HU proteins in E. coli?

Accepted Answer

They are histone-like proteins that help compact the bacterial chromosome.

Question 11

If a bacterial genome contains 20% cytosine (C), what is its GC content?

Accepted Answer

$$GC\ content = 2 	imes 20\% = 40\%$$

Question 12

Which of the following is a correct statement about cis-acting elements and trans-acting factors?

Accepted Answer

Cis-acting elements are DNA sequences, while trans-acting factors are usually proteins that interact with those sequences.

Question 13

A gene is identified as an open reading frame (ORF) in a bacterial genome. What does this mean?

Accepted Answer

It is a nucleotide sequence that can be translated into a protein without an in-frame stop codon interrupting the sequence.

Question 14

Which of the following best explains why knowing the sequence of one DNA strand allows you to determine the sequence of the complementary strand?

Accepted Answer

Because of complementary base pairing (A with T, G with C) and the antiparallel orientation of the two strands.

Question 15

Which of the following is NOT a feature typically found in a bacterial genome?

Accepted Answer

Introns within protein-coding genes

Question 16

A student is comparing the genomes of E. coli, yeast, and humans. Which of the following correctly ranks their gene densities from highest to lowest?

Accepted Answer

E. coli \u003e yeast \u003e\u003e human

Question 17

Which of the following is a function of the origin of replication (ori) in a bacterial genome?

Accepted Answer

It is a cis-acting DNA element where DNA replication is initiated.

Question 18

A researcher uses a genome database to study the ldhA gene in E. coli. Which of the following types of information can they obtain from the database?

Accepted Answer

Gene location, coding sequence, predicted protein sequence, and functional description

Question 19

Which of the following statements about genome size and gene number is correct?

Accepted Answer

A larger genome does not necessarily mean proportionally more genes, because gene densities vary among organisms.

Question 20

Which of the following best describes the direction of DNA synthesis by DNA polymerases?

Accepted Answer

DNA polymerases synthesize new DNA only in the $$5' \rightarrow 3'$$ direction.

Microbial Genetics: Structure and Organization of Microbial Genomes

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