Epigenetic control of gene expression

Question 1

Epigenetic changes

Answer 1

Changes in gene expression, possibly from changes in the environment such as diet, smoking and exercise of the organism.

Question 2

What result in epigenetic changes?

Answer 2

They result from changes in gene function without altercations in the DNA base sequence.

Question 3

How are epigenetic changes preserved?

Answer 3

When cells divide

Question 4

What can epigenetic changes be associated with?

Answer 4

They can be associated with:

• increased methylation of the DNA
• Decreased acetylation of associated histones

Question 5

Methylation? of DNA?

Answer 5

• The addition of Methyl groups to DNA
• Methylation of cytosine bases adjacent to guanine bases are known as CpG sites.
• This methylation prevents the binding of transcription factors and RNA polymerases
• Therefore, methylation prevents gene expression

Question 6

Acetylation? of Histones?

Answer 6

• DNA is packaged and coiled around proteins called histones.
• The addition of Acetyl groups to Histones
• The acetylation makes the DNA more accessible for transcription
• less acetylation = less expression or genes switching off.

Question 7

What is the role of proto-oncogenes?

Answer 7

They stimulate cell division

• A gene mutation can cause proto oncogenes to mutate into oncogenes
• This can permanently activate the receptor proteins on the cell surface membrane, causing cell division to be switched on in the absence of growth factors.
• This can also cause the oncogene to code for a growth factor, causing it to he produced in excessive amounts, therefore stimulating excessive cell division.

Question 8

Tl:Dr proto-oncogenes

Answer 8

A gene mutation causes protooncogenes to mutate into oncogenes, which can activate receptor proteins and code for growth factors, which can cause excessive cell division and therefore, cancer.

Question 9

What is the role of promotor regions at the tumor suppressor genes and protooncogenes?

Answer 9

Promotors: regions close to the start of a gene where RNA polymerase will bind to initiate transcription of the gene.

Question 10

What are tumor suppressor genes?

Answer 10

genes that inhibit cell division, a tumor suppressor gene that is mutated will become inactivated. and it stops inhibiting cell division. Causing an increase in cell division

Question 11

Promotor region at the tumor suppressor gene

Answer 11

• Too much methylation of promotors for TSG
• TSG will not be expressed
• Cell division unregulated
• Cancer

Question 12

Promotor region at the proto-oncogenes `

Answer 12

• Too little methylation of promotors for PG
• PG overexpressed
• Cancer

Question 13

Epigenetic treatments for cancer treatment

Answer 13

Enzymes responsible for methylation have drugs developed to inhibit them, they are approved.

It is possible to reactivate silenced tumor suppressor genes.