Epigenetic control of gene expression

Question 1

What is the process epigenetics?

Answer 1

-epigenetics is the proses by which environmental influences such as diet, stress, toxins, etc. can cause heritable changes in gene function and phenotypes without changing the base sequence of DNA

Question 2

What is the epigenome?

Answer 2

• the epigenome which are a layer of chemical tags determines the shape of the DNA-histone complex
• the epigenome, is flexible because its chemical tags respond to environmental changes by switching genes on or off due to signals recieved troughout the lifetime
• the epigenome of a cell is the accumulation of the signals it has received during its life time
• the environmental signals stimulates proteins to carry its message inside the cell from where it is passed by a series of other proteins into a nucleus
• here the message passes to a specific protein which can be attached to a specific sequence of bases on the DNA

Question 3

What is the DNA-histone complex (chromatic)?

Answer 3

• Heterochromatin: histones are tightly bound which condensed DNA to prevent transcription as transcription factors can’t get in
• euchromatin: histones are relaxed so transcription can occurs as it allows transcription factors in

Question 4

What is the decreased acetylation of associated histones?

Answer 4

• acetyl group is removed from the histone complex and donated to respiration which causes deacetylation
• which increases the positive charges on histones making them more condensed so transcription factors can’t get in
• so transcription can’t occur meaning, the gene is switched off

Question 5

How do you treat diseased with epigenetic therapy?

Answer 5

• these treatments use drugs to inhibit certain enzymes involved in either acetylation or DNA methylation
• for example drugs that inhibit enzymes that cause DNA methylation can reactivate genes that have been silenced
• epigenetic therapy must be specifically targeted on cancer cells
• if drugs were to affect normal cells they could activate gene transcription and make them cancerous, so causing the very disorder they were designed to cure
• another use of epigenetics in disease treatment has been the development of diagnostic tests that help to detect the early stages of diseased such as cancer, brain disorders and arthritis
• these tests can identify the level of DNA methylation and pistons acetylation at an early stage of disease
• this allows those with these diseased to seek early treatment and so have a better chance of cure

Question 6

What is the effect of RNA interference on gene expression?

Answer 6

• in eukaryotes and some prokaryotes the translation of mRNA produced by a gene can be inhibited by breaking mRNA down before its coded information can be translated into a polypeptide
• one type of small RNA molecule that may be involved is small interfering RNA (siRNA)

Question 7

How does the mechanism involving small double-stranded sections of siRNA operate?

Answer 7

• an enzyme cuts large double-stranded molecules of RNA into smaller sections called small interfering RNA (siRNA)
• one of the two siRNA strands combines with an enzyme
• the siRNA molecule guides the enzyme toil a messenger RNA molecule by pairing up its bases with the complementary ones on a section of the mRNA molecule
• once in position, the enzyme cuts the mRNA into smaller sections
• the mRNA is no longer capable of being translated into a polypeptide
• this means that the gene has not been expressed, that is, it has been blocked

Question 8

What is the prader-willi syndrome?

Answer 8

• epigenetic inheritance is thought to be involved in a rare genetic disease called Prader-Willi syndrome
• it is the result of seven genes on chromosomes 15 being deleted
• in most people, only one copy of the genes (usually from the farther) is expressed while the other copy of the genes (from the mother) is silenced through epigenetic inheritance
• this means that most people have one working and one epigenetically-silenced set of these genes
• however, if a mutation on chromosome 15 of the farther deletes the relevant seven games, any offspring produced will have one set of non-working genes and one set of epigenetically-silenced genes
• these individuals who’ll inherit prader-willi syndrome