Epigenetics

Question 1

What is imprinting?

Answer 1

A process in which chromosomes derived from each parent are uniquely chemically modified to affect gene expression

Leads to differential expression of genes on those chromosomes depending on parental origin

Often leads to gene being expressed on the chromosome from only 1 parent

Question 2

Basic epigenetic mechanisms

Answer 2

• DNA methylation
• Histone modification
• Chromatin remodeling
• RNA interference

Question 3

How many genes are imprinted? What proportion of the genome is this?

Answer 3

80%, 0.1-1% of all genes

Question 4

Imprinting disorders
- Prader Willi
- Angelman
- Beckwith-Wiedemann syndrome

Answer 4

Deletion in chromosome 15 occurs in:
- Paternal allele (Prader Willi)
- Maternal allele (Angelman)

Imprinting on chromosome 11

Question 5

Most maternal imprinting induces more/less growth

Paternal?

Answer 5

Maternal > less growth

Paternal > more growth

Question 6

Methylation on ___ = imprinting

When methylation is set, gene is/is not expressed

Answer 6

cytosine

methylation > gene NOT expressed

Question 7

Methylation prevents binding of ____ to promotor, shutting down ___

Answer 7

transcription factors

Gene expression

Question 8

70-80% of ___ sites are methylated/silenced in humans

20% remaining are clustered in sites called ___

Answer 8

CpG (methylated)

CpG islands (non-methylated), usually housekeeping genes

Question 9

Imprinting begins in the ___
Preserved throughout ___
then imprinting ___ occurs in early embryogenesis

Answer 9

the gametes
preserved throughout fertilization
resetting (erasure)

Question 10

What is the universal effector in DNA and histone methylation?

Answer 10

SAM (S adenosyl methonine) - universal methyl donor