Question 1

A researcher is studying a gene in humans that is only expressed when a specific transcription factor binds to an enhancer located 15 kb upstream of the gene's promoter. Which of the following best explains how this enhancer can regulate transcription from such a distant location?

Accepted Answer

DNA loops form to bring the enhancer-bound transcription factors into physical proximity with the promoter, facilitating interaction with the transcriptional machinery.

Question 2

In the lac operon, which combination of glucose and lactose availability will result in the STRONGEST transcription of the operon?

Accepted Answer

Glucose absent, lactose present

Question 3

A mutation in the lacI gene results in a nonfunctional repressor protein. What is the most likely effect on lac operon transcription?

Accepted Answer

The operon will be transcribed constitutively, regardless of lactose presence.

Question 4

Which of the following best describes the molecular effect of histone acetylation on gene expression?

Accepted Answer

Histone acetylation neutralizes the positive charge on histone tails, loosening DNA–nucleosome binding and promoting transcription.

Question 5

A yeast strain has a loss-of-function mutation in GAL80. What is the expected phenotype regarding GAL gene expression in the absence of galactose?

Accepted Answer

GAL genes will be constitutively expressed, even without galactose.

Question 6

Which of the following statements about DNA methylation in eukaryotes is correct?

Accepted Answer

DNA methylation at CpG islands generally silences gene expression by blocking transcription factor binding.

Question 7

A scientist is cloning a gene into a plasmid using a restriction enzyme that creates sticky ends. Why are sticky ends advantageous for this process?

Accepted Answer

Sticky ends allow the insert and vector to anneal via complementary base pairing, increasing the efficiency and specificity of ligation.

Question 8

Which of the following is a function of long noncoding RNAs (lncRNAs) in gene regulation?

Accepted Answer

They serve as decoys, scaffolds, guides, or antisense molecules to regulate chromatin and gene expression.

Question 9

Which of the following features is unique to eukaryotic gene regulation and not found in prokaryotes?

Accepted Answer

Chromatin remodeling and nucleosome repositioning

Question 10

A patient is found to have a disease caused by a mutation in a noncoding region of the genome, as identified by a GWAS study. What is the most likely mechanism by which this mutation contributes to disease?

Accepted Answer

The mutation disrupts a regulatory element, leading to abnormal gene expression.

Question 11

Which of the following best describes the difference between a reference genome and a pangenome?

Accepted Answer

A reference genome is a single consensus sequence, while a pangenome captures the full genetic diversity across many individuals.

Question 12

A gene is subject to genomic imprinting. Which of the following statements is TRUE regarding its expression?

Accepted Answer

Only one allele (either maternal or paternal) is expressed, depending on the parent of origin.

Question 13

Which of the following best explains why the lac operon is transcribed at a LOW level when both glucose and lactose are present?

Accepted Answer

CAP is not bound to the promoter due to low cAMP, so positive regulation is off, resulting in low transcription even though the repressor is not blocking.

Question 14

A transcription factor has a mutated DNA-binding domain but an intact activation domain. What is the most likely consequence for gene regulation?

Accepted Answer

The transcription factor will fail to bind its target DNA sequence and cannot activate transcription.

Question 15

Which of the following best describes the function of the CAP/cAMP complex in the lac operon?

Accepted Answer

It acts as an activator, enhancing transcription when glucose is absent and cAMP is high.

Question 16

A researcher is using PCR to amplify a DNA fragment. Which of the following is essential for the exponential amplification of the target sequence?

Accepted Answer

A thermostable DNA polymerase that can withstand repeated heating cycles.

Question 17

Which of the following best describes the role of the TFIID protein in eukaryotic transcription initiation?

Accepted Answer

TFIID binds the TATA box in the promoter, serving as the first step in assembling the pre-initiation complex.

Question 18

A mutation in the operator region of the lac operon prevents the repressor from binding. What is the expected effect on lac operon transcription?

Accepted Answer

Constitutive transcription of the operon, regardless of lactose presence.

Question 19

Which of the following best explains why restriction enzymes are useful in molecular cloning?

Accepted Answer

They cut DNA at specific palindromic sequences, generating defined fragments with sticky or blunt ends for ligation.

Gene Regulation, Epigenetics, and Biotechnology: Study Guide for Genetics

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