Question 1

Which of the following statements best describes the difference between prokaryotic and eukaryotic genomes?

Accepted Answer

Prokaryotic genomes are usually circular and consist of a single chromosome, whereas eukaryotic genomes are linear and consist of multiple chromosomes.

Question 2

Which enzyme is responsible for synthesizing the leading strand during DNA replication, and what is the direction of synthesis?

Accepted Answer

DNA polymerase III; synthesis occurs in the $5' \rightarrow 3'$ direction.

Question 3

A mutation changes the codon $UAC$ (tyrosine) to $UAA$ (stop codon). What type of mutation is this, and what is its likely effect on the protein?

Accepted Answer

Nonsense mutation; the protein will be truncated and likely nonfunctional.

Question 4

Which of the following best explains why the traditional definition of species based on reproductive isolation does not apply to Bacteria and Archaea?

Accepted Answer

Bacteria and Archaea reproduce asexually and can exchange genes horizontally, making reproductive isolation an unsuitable criterion.

Question 5

Which of the following mechanisms is NOT a form of horizontal gene transfer in bacteria?

Accepted Answer

Binary fission

Question 6

In the lac operon, which molecule acts as the inducer and what is its effect?

Accepted Answer

Lactose; it binds to the repressor, causing it to release from the operator and allowing transcription.

Question 7

Which DNA repair mechanism in prokaryotes uses the enzyme photolyase to directly reverse UV-induced thymine dimers?

Accepted Answer

Photoreactivation

Question 8

A bacterium is exposed to an antibiotic. Over time, it acquires resistance through a mutation and horizontal gene transfer. Which process best describes this scenario?

Accepted Answer

Natural selection acting on genetic variation created by mutation and horizontal gene transfer.

Question 9

Which of the following statements about viral genomes is correct?

Accepted Answer

Viral genomes can be composed of dsDNA, ssDNA, dsRNA, or ssRNA.

Question 10

Which enzyme is required for retroviruses to replicate their genome, and what is its function?

Accepted Answer

Reverse transcriptase; synthesizes DNA from an RNA template.

Question 11

Which of the following best describes the role of cyanobacteria in the oxygenation of Earth's atmosphere?

Accepted Answer

Cyanobacteria perform photosynthesis, releasing oxygen as a byproduct.

Question 12

Which of the following is a representative thermophile, and what is its unique adaptation?

Accepted Answer

Sulfolobus acidocaldarius; thrives in high temperatures and acidic environments.

Question 13

Which of the following statements about the lytic and lysogenic cycles of bacteriophages is correct?

Accepted Answer

The lysogenic cycle involves integration of viral DNA into the host genome, allowing the virus to remain dormant, while the lytic cycle results in immediate destruction of the host cell.

Question 14

Which of the following best describes the function of the viral capsid?

Accepted Answer

The capsid contains the viral genome and protects it from environmental damage.

Question 15

A patient is diagnosed with Creutzfeldt-Jakob disease. Which infectious agent is responsible, and what is its mechanism of action?

Accepted Answer

Prion; induces misfolding of normal proteins in the brain.

Question 16

Which of the following best explains why 16S rRNA is used to compare evolutionary relationships among prokaryotes?

Accepted Answer

16S rRNA is highly conserved and present in all prokaryotes, allowing for comparison across diverse taxa.

Question 17

Which of the following best describes the relationship between genotype and phenotype?

Accepted Answer

Genotype determines phenotype through the expression of genes as proteins.

Question 18

Which of the following is a plausible outcome of a frameshift mutation in a protein-coding gene?

Accepted Answer

The protein will have a completely altered amino acid sequence downstream of the mutation, often resulting in loss of function.

Question 19

Which of the following best describes the process of bacterial conjugation?

Accepted Answer

Transfer of DNA from one bacterium to another via a pilus, often involving F plasmids.

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