Question 1

Which of the following best describes the difference between a nucleoside and a nucleotide?

Accepted Answer

A nucleotide contains a phosphate group, a pentose sugar, and a nitrogenous base, while a nucleoside lacks the phosphate group.

Question 2

Why do purines always pair with pyrimidines in the DNA double helix?

Accepted Answer

Pairing a purine with a pyrimidine maintains a uniform width of the DNA helix, allowing for stable hydrogen bonding.

Question 3

Which of the following statements about prokaryotic and eukaryotic genomes is correct?

Accepted Answer

Prokaryotic chromosomes are typically circular and found in the nucleoid, while eukaryotic chromosomes are linear and found in the nucleus.

Question 4

Which of the following best explains why DNA replication is described as 'semiconservative'?

Accepted Answer

Each new DNA molecule consists of one original (parental) strand and one newly synthesized strand.

Question 5

During bacterial DNA replication, which enzyme is responsible for removing supercoils ahead of the replication fork?

Accepted Answer

Topoisomerase (including gyrase)

Question 6

Which of the following is a key difference between DNA replication in prokaryotes and eukaryotes?

Accepted Answer

Eukaryotes have multiple origins of replication per chromosome and use histones for DNA packaging.

Question 7

Which of the following best describes the central dogma of molecular biology?

Accepted Answer

DNA is transcribed into RNA, which is then translated into polypeptides.

Question 8

Which of the following events occurs during the elongation phase of transcription in prokaryotes?

Accepted Answer

Ribonucleotides align with their complementary DNA bases, and RNA polymerase links them in the 5' to 3' direction.

Question 9

Which of the following is NOT a post-transcriptional modification of eukaryotic mRNA?

Accepted Answer

Concurrent translation of mRNA during transcription

Question 10

Which of the following statements about the lac operon is correct?

Accepted Answer

The lac operon is an inducible operon activated by the presence of lactose and cAMP-CAP complex.

Question 11

A mutation changes a codon from UAU (tyrosine) to UAA (stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 12

Which of the following best describes generalized transduction?

Accepted Answer

Transfer of random donor DNA segments by a bacteriophage to a recipient cell.

Question 13

Which of the following is a function of DNA methylation in bacteria?

Accepted Answer

Protection against viral infection

Question 14

Which of the following mechanisms of horizontal gene transfer in bacteria requires cell-to-cell contact and an F plasmid?

Accepted Answer

Conjugation

Question 15

A chemical mutagen that mimics a normal nucleotide and is incorporated into DNA during replication is best described as:

Accepted Answer

A nucleotide analog

Question 16

Which of the following is a reason why translation can begin before transcription is complete in prokaryotes but not in eukaryotes?

Accepted Answer

Eukaryotic transcription and translation are separated by the nuclear envelope.

Question 17

Which of the following best describes a transposon?

Accepted Answer

A segment of DNA that can move from one location to another within a genome, often causing frameshift mutations.

Question 18

Which of the following is a correct statement about repressible operons?

Accepted Answer

They are transcribed continually until deactivated by a repressor, often in response to the presence of the pathway's end product.

Question 19

Which of the following best explains why mutations in DNA are generally more deleterious than errors in RNA transcription?

Accepted Answer

DNA mutations are permanent and heritable, while RNA errors are temporary and not passed to progeny.

Question 20

Which of the following is a function of regulatory RNAs such as microRNAs (miRNAs) in gene expression?

Accepted Answer

They bind to complementary mRNA and inhibit its translation.

Microbial Genetics: Structure, Function, and Regulation of Genetic Material

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