Question 1

Which of the following statements best explains why skin cell nuclei from an adult frog can give rise to a normal tadpole when injected into an enucleated frog egg, as shown in the experiment by Briggs and King (1952)?

Accepted Answer

Skin cell nuclei retain all the genetic information necessary to direct the development of an entire organism.

Question 2

Transcription initiation is often considered the most critical and rate-limiting step in regulating gene expression. Which of the following best explains why?

Accepted Answer

Initiation requires the assembly of multiple transcription factors and RNA polymerase at the promoter, making it a tightly regulated checkpoint.

Question 3

Which of the following best describes the role of DNA methylation in gene regulation?

Accepted Answer

DNA methylation typically decreases transcription by adding methyl groups to cytosine bases in CpG islands near promoters.

Question 4

A researcher finds that a gene is highly methylated at its promoter region in a certain cell type. What is the most likely effect on the expression of this gene?

Accepted Answer

The gene will be transcriptionally silenced or expressed at very low levels.

Question 5

Which of the following is an example of an epigenetic change?

Accepted Answer

Methylation of cytosine bases in DNA that alters gene expression without changing the DNA sequence.

Question 6

In the context of maternal care in rats, which of the following is TRUE regarding the relationship between maternal behavior and epigenetic regulation of the glucocorticoid receptor (GR) gene?

Accepted Answer

High maternal care leads to low promoter methylation and high GR expression, resulting in better stress adaptation.

Question 7

Which of the following best describes the concept of 'Adverse Childhood Experiences' (ACEs) and their potential impact on future generations?

Accepted Answer

ACEs can increase the risk of negative health outcomes in both the individual and their descendants, potentially through epigenetic mechanisms.

Question 8

The human metallothionein 2A (MT2A) gene is expressed at low levels in all cells but is highly upregulated in response to heavy metals. Which of the following best explains this regulation?

Accepted Answer

MTF-1, a metal-inducible transcription factor, binds to enhancer elements and increases transcription in response to heavy metals.

Question 9

Why are 'housekeeping genes' typically found with unmethylated CpG islands near their promoters?

Accepted Answer

Unmethylated CpG islands allow for continuous transcription necessary for basic cellular functions.

Question 10

A mutation in the MITF gene results in reduced expression of tyrosinase and related proteins in the developing eye of mice. What is the most likely explanation for this observation?

Accepted Answer

MITF is a transcription factor that binds to enhancer regions of tyrosinase genes, promoting their expression.

Question 11

Which of the following best describes the function of a basic helix-loop-helix (bHLH) transcription factor, such as MITF?

Accepted Answer

It binds to specific DNA sequences and recruits co-activators, such as histone acetyltransferases, to promote gene expression.

Question 12

If a gene is only expressed in the brain and limb, which of the following is the most likely explanation?

Accepted Answer

The gene has tissue-specific enhancers that are active only in brain and limb cells.

Question 13

Which of the following equations correctly represents the probability of a child experiencing four or more ACEs if their parent has four or more ACEs, given a 3.25-fold increased risk?

Accepted Answer

$$P_{child} = 3.25 	imes P_{baseline}$$

Question 14

Which of the following best explains why environmental factors such as nutrition or stress can have long-term effects on gene expression?

Accepted Answer

They can induce epigenetic changes, such as DNA methylation, that alter gene expression patterns without changing the DNA sequence.

Question 15

A scientist observes that a certain gene is expressed in the pancreas and lens/cornea of a mouse embryo, but not in other tissues. Which regulatory elements are most likely responsible for this pattern?

Accepted Answer

Tissue-specific enhancers located near the gene that are active in the pancreas and lens/cornea.

Question 16

Which of the following best describes the relationship between enhancer elements and gene expression?

Accepted Answer

Enhancers are DNA sequences that increase the transcription of associated genes when bound by specific transcription factors.

Question 17

Which of the following is a likely consequence of a loss-of-function mutation in a transcription factor that normally recruits histone acetyltransferase to a gene's enhancer?

Accepted Answer

Reduced gene expression due to decreased chromatin accessibility.

Gene Regulation and Epigenetics: Mechanisms and Examples in Eukaryotes

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