Epigenetics

Question 1

What is epigenetics?

Answer 1

Changes in gene expression that result from mechanisms other than changes in the genes - in the DNA or genome

Question 2

What is a person’s epigenome?

Answer 2

Hereditary information encoded in their DNA - the sum of all factors that determine when, where, which genes are ‘switched on’ or expressed.

Question 3

How can a person’s genome be changed?

Answer 3

Exposure to certain environmental stimulus - severe stress, nutritional factors, toxins/drugs

Question 4

What does the modified histone do?

Answer 4

Ensures that a stem cell that differentiated into a liver cell would remain a liver cell and not revert to being a stem cell.

Question 5

What other histone modifications may occur?

Answer 5

1. Acetylation
2. Methylation

Question 6

What is acetylation?

Answer 6

The addition of an acetyl group to a histone protein so that gene expression is enhanced.

• Reduces the attraction between histones and DNA and relaxing chromatin structure.

Question 7

What does acetylation promote?

Answer 7

This promotes transcription by allowing RNA polymerase access, enhancing gene expression.

Question 8

What is methylation?

Answer 8

The addition of a methyl group to a DNA molecule that results in inhibition of gene expression

Question 9

Where does DNA methylation occur?

Answer 9

Usually occurs on the sites on DNA where cytosine nucleotide is adjacent to a guanine nucleotide – CpG sites.

• Cytosine-phosphorous-guanine

Question 10

What is the effect of histone methylation on the transcription of genes?

Answer 10

Histone methylation either increases/decreases transcription of genes depending on where and how many methyl groups attach.

Question 11

How does DNA Methylation inhibit gene expression?

Answer 11

By restricting access to RNA polymerase.

Question 12

How can Methylation increase transcription?

Answer 12

If the methylation causes the chromatin structure to relax, it will increase.