Question 1

Which of the following best describes the effect of DNA methylation at CpG islands in gene promoters?

Accepted Answer

It decreases gene expression by silencing transcription.

Question 2

During DNA replication, what is the state of methylation immediately after synthesis, and how is full methylation restored?

Accepted Answer

The parental strand is methylated and the new strand is unmethylated (hemimethylated); maintenance methyltransferase methylates the new strand.

Question 3

Which of the following is a property of long noncoding RNAs (lncRNAs) that distinguishes them from mRNAs?

Accepted Answer

They bind chromatin-modifying enzymes and regulate gene expression.

Question 4

Genomic imprinting is best described as:

Accepted Answer

The silencing of certain genes depending on which parent passes them on, without altering the DNA sequence.

Question 5

A mouse inherits an Igf2+ allele from its father and an Igf2- allele from its mother. What is the expected phenotype regarding birth weight?

Accepted Answer

Normal birth weight, because only the paternal allele is expressed.

Question 6

Which syndrome results from the loss of function of the paternal allele at chromosome 15q11-q13, given that the maternal allele is normally imprinted?

Accepted Answer

Prader–Willi syndrome

Question 7

What is the role of XIST in X chromosome inactivation in female mammals?

Accepted Answer

It produces a long noncoding RNA that coats and silences the inactive X chromosome.

Question 8

Which of the following best explains why monozygotic twins can have different phenotypes despite identical DNA sequences?

Accepted Answer

They have greater differences in epigenetic marks than in DNA base sequence.

Question 9

Which of the following is true regarding histone modifications during DNA replication?

Accepted Answer

Each daughter chromosome inherits about half of its parent’s modified histones, and the pattern is restored by modifying enzymes.

Question 10

Which of the following best describes the relationship between the genome and the epigenome?

Accepted Answer

The genome is the DNA sequence, and the epigenome is the set of chemical modifications to DNA and histones that regulate gene expression.

Question 11

Which of the following equations correctly represents the methylation of cytosine to 5-methylcytosine?

Accepted Answer

$$\mathrm{Cytosine} + \mathrm{CH}_3 \xrightarrow{\mathrm{Methyltransferase}} \mathrm{5	ext{-}Methylcytosine}$$

Question 12

A gene is expressed in lung tissue but not in heart tissue. What is the most likely methylation state of its promoter in these tissues?

Accepted Answer

The promoter is hypomethylated in lung cells and hypermethylated in heart cells.

Question 13

Which of the following is a real-life example of epigenetic regulation affecting phenotype?

Accepted Answer

Variation in coat color in calico cats due to random X chromosome inactivation.

Question 14

Which of the following best explains why Beckwith–Weidemann syndrome (BWS) is considered an imprinting disorder?

Accepted Answer

It is caused by abnormal patterns of DNA methylation resulting in altered gene expression.

Question 15

Which of the following statements about monoallelic gene expression is correct?

Accepted Answer

Only one allele of a gene is expressed, while the other is silenced, as seen in genomic imprinting.

Question 16

Which process ensures that one X chromosome is inactivated in each female cell?

Accepted Answer

Expression of XIST lncRNA from the X-inactivation center.

Question 17

Which of the following best describes the inheritance of epigenetic marks during cell division?

Accepted Answer

DNA methylation and histone modifications can be faithfully inherited by daughter cells.

Question 18

Which of the following is NOT a mechanism of epigenetic gene regulation?

Accepted Answer

Point mutation in a coding region

Epigenetics and Gene Regulation in Eukaryotes

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