Epigenetic Control of Gene Expression

Question 1

What is meant by epigenetics?

Answer 1

A field of science that refers to how environmental influences (Diet, stress, toxins etc:) affect genetic inheritance of an organism’s offspring.

Question 2

What is the epigenome?

Answer 2

-The layer of chemical tags that are attached to DNA and histones.
-The epigenome determines the shape of shape of the DNA-histone complex.
-It can keep inactive genes tightly packed so that they avoid being read (Epigenetic silencing)

Question 3

What is the effect of epigenetic factors on DNA and histones?

Answer 3

As environmental factors change, the wrapping and unwrapping of DNA is altered, causing different genes to be expressed and in-expressed.

Question 4

What is the effect of “decreased acetylation of histones”?

Answer 4

-Acetylation is the process whereby an acetyl group is added to the histones in DNA.

-Deacetylation is the opposite of this, and increases the positive charges on histones causing a stronger association between histones and DNA, making DNA less accessible to transcription factors.

-This switches off the gene.

Question 5

What is the effect of “Increased methylation of DNA”?

Answer 5

-The addition of a methyl group to a molecule
-This: (1) Prevents the binding of transcriptional factors to the DNA (2) Attracting proteins that condense DNA-histone complex making the DNA inaccessible to transcription factors

Question 6

What is the effect of RNA interference on gene expression?

Answer 6

-An enzyme cuts large, double stranded RNA molecules into smaller sections called siRNA

-One of these strands combines with an enzyme

-The siRNA molecule guides said enzyme to an mRNA by complementary base pairing with a section on mRNA

-The enzyme can then cut the mRNA into smaller mRNA sections

-The mRNA can no longer be capable of being translated into a poly peptide, hence blocking the gene