3.4.4 - Epigenetics

Question 1

What Is Epigenetics?
(2 Points)

Answer 1

~ Is the control of gene expression by factors other than an individuals DNA sequence.

~ It involves the switching on and off of genes, without changing the actual genetic code.

Question 2

How Can Chromatin Be Chemically Modified To Alter Gene Expression?
(2 Points)

Answer 2

~ Methylation of DNA.

~ Histone modification.

Question 3

Describe The Process Of DNA Methylation
(4 Points)

Answer 3

~ A methyl group is added to DNA to change the activity of a gene.

~ The methyl group is always added to the CpG site, where the cytosine and the guanine bases are next to each other.

~ Suppresses the transcription of the affected gene by inhibiting the binding of transcription factors and enzymes needed for transcription (RNA polymerase).

~ Gene is repressed.

Question 4

What Are Histones?

Answer 4

Proteins that DNA wraps around to form chromatin.

Question 5

Describe Chromatin
(2 Points)

Answer 5

~ Can be highly condensed or less condensed.

~ How condensed it is affects the accessibility of the DNA and whether or not the proteins and enzymes needed for transcription can bind to it.

Question 6

What Happens When Histones Are Acetylated?
(4 Points)

Answer 6

~ Acetyl groups are added to the histones.

~ Chromatin is less condensed.

~ Proteins involved in transcription can bind to the DNA.

~ Allowing genes to be transcribed (Activated).

Question 7

What Happens When Acetyl Groups Are Removed From The Histones?
(3 Points)

Answer 7

~ Chromatin becomes highly condensed.

~ Genes in the DNA cannot be transcribed because RNA polymerase cannot bind to the them.

~ Genes are repressed.