3.4.4 - Epigenetics

Question 1

What Is Epigenetics?
(3 Points)

Answer 1

~ Can occur in response to changes in the environment.

~ Determines whether certain genes are expressed, altering the phenotype.

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

Question 2

How Does Epigenetics Work?
(2 Points)

Answer 2

~ Attaching or removing chemical groups to or from the DNA.

~ Altering how easy it is for enzymes and proteins needed for transcription to transcribe the genes.

Question 3

Describe Nuclear DNA In Eukaryotic Cells
(2 Points)

Answer 3

~ Nuclear DNA is wrapped around proteins called histones to form chromatin.

~ Chromatin can then be chemically modified to alter gene expression.

Question 4

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

Answer 4

~ Methylation of DNA -> chemical addition of CH3 groups.

~ Acetylation of amino acid tails -> histone modification.

Question 5

Describe The Process Of DNA Methylation
(4 Points)

Answer 5

~ 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 6

What Are Histones?

Answer 6

Proteins that DNA wraps around to form chromatin.

Question 7

Describe Chromatin
(2 Points)

Answer 7

~ 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 8

What Happens When Histones Are Acetylated?
(4 Points)

Answer 8

~ 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 9

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

Answer 9

~ Chromatin becomes highly condensed.

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

~ Genes are repressed.

Question 10

Describe How Epigenetic Changes Can Be Passed On After Cell Division
(2 Points)

Answer 10

~ When a cell divides or replicates, epigenetic changes to its gene expression may be passed onto the daughter cells.

~ If passed on it means certain genes may be activated or inactivated.