Question 1

Which of the following best describes the structural difference between bacterial and eukaryotic chromosomes?

Accepted Answer

Bacterial chromosomes are circular and typically have a single origin of replication, while eukaryotic chromosomes are linear and contain multiple origins, centromeres, and telomeres.

Question 2

Negative supercoiling of DNA is important because it:

Accepted Answer

Promotes DNA strand separation, aiding replication and transcription.

Question 3

Which enzyme introduces negative supercoils into DNA?

Accepted Answer

DNA gyrase

Question 4

Transposable elements (TEs) can impact the genome by:

Accepted Answer

Increasing genome size, altering gene regulation, and driving genetic diversity.

Question 5

Which type of transposable element contains only the genes required for transposition?

Accepted Answer

Insertion sequence

Question 6

In the lac operon, what is the role of allolactose?

Accepted Answer

It acts as an inducer, binding to the repressor and allowing transcription.

Question 7

Which of the following best explains attenuation in the trp operon?

Accepted Answer

It is a mechanism where transcription is terminated prematurely based on tryptophan levels.

Question 8

A feedback inhibition mechanism in posttranslational regulation involves:

Accepted Answer

The final product of a pathway inhibiting an early enzyme.

Question 9

Which of the following is a correct example of a riboswitch?

Accepted Answer

TPP riboswitch regulates thiamin pyrophosphate synthesis by changing RNA conformation upon ligand binding.

Question 10

Which statement about gene regulation is TRUE?

Accepted Answer

Gene regulation ensures proteins are produced only when needed, conserving energy.

Question 11

Which molecule acts as a repressor in transcriptional regulation?

Accepted Answer

A protein that binds to DNA and inhibits transcription.

Question 12

Which of the following is a plausible consequence of a mutation that disables the topoisomerase I enzyme in bacteria?

Accepted Answer

Accumulation of excessive negative supercoiling, potentially hindering replication and transcription.

Question 13

A scientist discovers a transposable element in a bacterial genome that carries an antibiotic resistance gene. What type of TE is this most likely to be?

Accepted Answer

Composite transposon

Question 14

Which of the following equations correctly represents the relationship between the linking number ($$L$$), twist ($$T$$), and writhe ($$W) in $$DNA topology?

Accepted Answer

$$L = T + W$$

Question 15

If a bacterial cell has a circular chromosome with a single origin of replication, which process ensures the chromosome is properly segregated during cell division?

Accepted Answer

Chromosome compaction and replication origin function

Question 16

Which of the following mechanisms can inhibit translation by preventing ribosome access to mRNA?

Accepted Answer

Repressors binding to mRNA or formation of secondary structures

Question 17

Jacob and Monod's experiments on the lac operon demonstrated that:

Accepted Answer

Diffusible repressor proteins control gene expression.

Question 18

Which of the following is an example of a covalent modification in posttranslational regulation?

Accepted Answer

Phosphorylation of a protein

Question 19

A mutation in the trp operon prevents the formation of stem-loop structures in mRNA. What is the most likely consequence?

Accepted Answer

Transcription termination by attenuation will be impaired, leading to increased trp operon expression.

Question 20

Which of the following best describes the function of activators in transcriptional regulation?

Accepted Answer

Bind to DNA to enhance transcription (positive control)

Molecular Genetics: Chromosome Structure, Transposable Elements, and Gene Regulation

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