Question 1

Which of the following best describes the effect of adding an inducer to an E. coli culture containing the lac operon, as shown in the first image?

Accepted Answer

The inducer binds to the repressor, causing it to release from the operator, which increases β-galactosidase production.

Question 2

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

Accepted Answer

It is an inducer that binds to the repressor, causing a conformational change that prevents the repressor from binding the operator.

Question 3

Which of the following best explains why total bacterial protein increases after the addition of an inducer in the first image?

Accepted Answer

The increase in β-galactosidase allows the cell to metabolize lactose, providing more energy for overall protein synthesis.

Question 4

Which of the following best describes the regulatory logic of the lac operon in the presence of glucose and absence of lactose?

Accepted Answer

The operon is repressed because the repressor remains bound to the operator and CAP is inactive.

Question 5

Which structural motif is most commonly found in bacterial DNA-binding regulatory proteins?

Accepted Answer

Helix-turn-helix

Question 6

In the context of the trp operon, what is the effect of high tryptophan levels on the leader region?

Accepted Answer

It causes the formation of a termination stem-loop, halting transcription.

Question 7

Which of the following is a key difference between positive and negative control of transcription?

Accepted Answer

Negative control involves repressors that block transcription, while positive control involves activators that enhance transcription.

Question 8

In the second image (heatmap of intra-chromosomal interactions), what do the 'hot' squares along the diagonal represent?

Accepted Answer

Regions of high spatial interaction between adjacent chromosomal segments, indicating topologically associating domains (TADs).

Question 9

What is the role of formaldehyde in generating the data shown in the second image (chromosome conformation capture heatmap)?

Accepted Answer

It crosslinks interacting chromatin regions, preserving their spatial proximity for analysis.

Question 10

Which of the following best describes the hourglass-shaped region in the third image (synteny plot between human and chimpanzee chromosome 2)?

Accepted Answer

A region of conserved synteny with an inversion event between the two species.

Question 11

Which of the following is a feature of open chromatin in eukaryotes?

Accepted Answer

Low levels of DNA methylation and high gene expression.

Question 12

Which histone modification is most commonly associated with active transcription in euchromatin?

Accepted Answer

Histone acetylation

Question 13

Which of the following best describes the difference between forward and reverse genetics?

Accepted Answer

Forward genetics starts with a phenotype and identifies the gene; reverse genetics starts with a known gene and investigates its phenotype.

Question 14

Which enzyme is critical for covalently joining a DNA fragment into a plasmid vector during molecular cloning?

Accepted Answer

DNA ligase

Question 15

What is the main difference between a genomic library and a cDNA library?

Accepted Answer

A genomic library contains all DNA sequences from the genome, while a cDNA library contains only sequences derived from mature mRNA.

Question 16

Which of the following is a challenge of using mRNA sequencing to annotate a eukaryotic genome?

Accepted Answer

It may miss genes that are not expressed under the sampled conditions.

Question 17

If an individual receives a genetic test result for a cancer-associated mutation with an odds ratio (OR) of 2.7, what does this mean?

Accepted Answer

The individual's risk of developing cancer is 2.7 times higher than someone without the mutation.

Question 18

Why is TP53 referred to as the 'guardian of the genome'?

Accepted Answer

It encodes a protein that regulates cell cycle arrest, DNA repair, and apoptosis in response to DNA damage.

Question 19

Which of the following best describes the difference between chromothripsis and MMBIR as mechanisms of genome rearrangement in cancer?

Accepted Answer

Chromothripsis is a 'shatter and stitch' mechanism causing massive rearrangements in one event, while MMBIR involves template switching during DNA replication.

Step-by-Step Guidance for Genetics Exam Review: Gene Expression, Regulation, and Genomics

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