Epigenetics

Question 1

Epigenetics

Answer 1

A change in phenotype that doesn’t result from a change in the sequence of a gene
Change is heritable
Caused by switching on or off parts of genome in response to environment

Question 2

Gene silencing

Answer 2

Interplay between DNA methylation, histone acetlyation, and RNA interference to completely shut down a gene

Question 3

CpG island

Answer 3

Region of DNA with lots of cytosines followed by guanines

Methylation of region causes gene to be silenced

Question 4

Methylation

Answer 4

CpG island is methylated, causing gene to be silenced
Methyl groups physically block transcriptional machinery
Can sometimes recruit histone deacetylases to modify histone tails

Question 5

Histone tail modification

Answer 5

Histone acetyltransferases (HATs) cause masking of positive charge on histone tails, making DNA accessible
Heritable change
Process is reversible by histone deacetylases (HDACs), recruited by DNA methylation

Question 6

Regulatory RNAs

Answer 6

micro RNA and short interfering RNA

Control target mRNA degradation

Question 7

RNA interference steps

Answer 7

1. miRNA is transcribed
2. miRNA is processed into shRNA (short hairpin RNA)
3. RISC (RNA interference silencing complex) recognizes shRNA and picks it up
4. RISC complex binds to mRNA
5. RISC complex cuts off mRNA’s poly A tail
6. mRNA is degraded