lecture 42

Question 1

what are some roles of epigenetics?

Answer 1

1. regulation of gene expression by repression
2. cellular differentiation by gene repression
3. dosage compensation (genes)
4. modulation of gene expression based on the environment
5. whole chromosome inactivation

Question 2

what enzyme methylates DNA thus repressing certain genes?

Answer 2

DNA methyltransferase

Question 3

What DNA base is usually methylated and where?

Answer 3

cytosine and one the 5th carbon

Question 4

How does methylation occur?

Answer 4

1. Dnmt3 methylated unmethylated DNA
2. MeCP2 recruites either HDAC1 or Dnmt1
   3) HDAC1 deacetylates histones
   4) Dnmt1 methylates hemimethylated DNA

Question 5

what does deacetylation of the histone do?

Answer 5

makes the histone more positive, thus the DNA binds tighter

Question 6

What can occur due to a Dnmt3 gene mutation?

Answer 6

ICF syndrome (hypomethylation)

Question 7

what are some symptoms of ICF?

Answer 7

facial dysmorphism
mental retardation
constant decrease in IgA

Question 8

How does rhett syndrome occur genetically?

Answer 8

A mutation in the MeCP2 protein

Question 9

How are globin genes regulated?

Answer 9

DNA methylation

happens during fetal development

Question 10

when is gene imprinting established?

Answer 10

1. When primordial germ cells enter gametogenesis the genetic imprint is erased.
2. During gametogenesis a male specific imprint is established in sperm and a female specific imprint is established in oocytes.
3. Shortly after fertilization the genome becomes hypomethylated but imprinted genes remain methylated.
4. Genome methylation increases during embryonic development and cell differentiation.

Question 11

imprinting and prader-willi?

Answer 11

the maternal copy of the snrpn gene is imprinted

Question 12

imprinting and angleman’s

Answer 12

the paternal copy of the UBE3A gene is imprinted

Question 13

what does the addition of the two drugs decitabine and 5-azacytidine cause and why?

Answer 13

They lead to hypomethylation because they cannot be methylation due to the N at position 5.

Question 14

What is P15?

Answer 14

it is a tumor suppressor gene!

decitabine can be used to hypomethylate and prevent cancer formation when P15 is not working properly.

Question 15

Children of IVF have a much greater risk of what disease?

Answer 15

Beckwith-Wiedemann syndrome (BWS)

Question 16

How to detect BWS by lab techniques?

Answer 16

abnormal methylation will be seen

more cuts = less methylation
less cuts = more methylation

Question 17

What environmental factors influence epigenetic changes?

Answer 17

1. site of fertilization
2. toxins
3. maternal care
4. diet (folate)
5. hypoxia

Question 18

what is the gamete theory of transgenerational epigenetics?

Answer 18

what you do has an impact on your children and your grandchildren