Epigenetic Phenomena

Question 1

Explain epigenetics

Answer 1

Study of heritable changes in a population without change in DNA

Question 2

Explain the process of de novo methylation and maintenance.

Answer 2

1. DNMT3a methylates DNA strand
2. DNA is pulled apart and replicated.
3. for a brief moment, DNA daughter strands can act as places to signal repair.
4. DNMT1 (maintence) comes along and methylates.
5. methylcytosine binding proteins bind and repress transcription.

Question 3

What is Rett Syndrome?

Answer 3

Mutation in MECP2 methylcystosine binding protein; x-dom disease

Question 4

Explain the significance of CPG islands. Where are they found?

Answer 4

These are active regions randomly located in a sea of inactive CPGs. These areas are prone to methylation.

found near the 5’ region of genes.

Question 5

Hypermethylation vs hypomethylation

Answer 5

Hypermethylation: silences DNA
Hypomethylation: activates DNA

Question 6

Histone Modification Steps

Answer 6

1. De-acetylated by HDACS
2. methylation
3. methlyated histones bind HPI proteins
4. HPI proteins recruit histone methylases
5. continue until they reach a barrier

Question 7

Explain the timing of imprinting?

Answer 7

development: cell-type specific
gametogenesis: parent of origin specific imprint

Question 8

When is imprinting reversible?

Answer 8

during gametogenesis when the parent of origin imprint needs to be eared and rewritten

Question 9

Basic steps of X chrom inactivation?

Answer 9

1. XIC center on x-chrom

2. contains XIST which gets activated and mediates inactivation of x chrom by methylation

Question 10

What is uniparental disomy?

Answer 10

leads to problems with gene dosage; starts with a trisomy 21 cell; results in either a spontaneous abortion, mosaicism or uniparental disomy

Question 11

What is a disease that represents uniparental disomy?

Answer 11

Beckwith-Wiedemann Syndrome; results when child inherits 2 copies of paternal chrom 11; leads to overabundance of insulin-like growth factor 2, which leads to kidney, adrenal, and liver problmes

Question 12

What is the disease due to a deletion of parental chrom 15?

Answer 12

Prader-Willi: characterized by obsessive eating, hypogonadadism

Question 13

What disease is due to a deletion of maternal chrom 15?

Answer 13

Angelman: obsessive laughter; unusual facial features, etc

Question 14

Systemic Lupus Erythematosus?

Answer 14

hypomethylation and leads to re-expression of silenced genes

Question 15

What are HDAC inhibitors?

Answer 15

promotes histone hyperacetylation and gene re0expression in chronic lymphocytic leukemia

Question 16

What are DNMT inhibitors? example?

Answer 16

causes hypomethylation of the genome; (5-azacytidine); approved for the therapy of acute myeloid leukemia