Flashcards in lecture 42 Deck (18)
what are some roles of epigenetics?
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
what enzyme methylates DNA thus repressing certain genes?
What DNA base is usually methylated and where?
cytosine and one the 5th carbon
How does methylation occur?
1. Dnmt3 methylated unmethylated DNA
2. MeCP2 recruites either HDAC1 or Dnmt1
3) HDAC1 deacetylates histones
4) Dnmt1 methylates hemimethylated DNA
what does deacetylation of the histone do?
makes the histone more positive, thus the DNA binds tighter
What can occur due to a Dnmt3 gene mutation?
ICF syndrome (hypomethylation)
what are some symptoms of ICF?
constant decrease in IgA
How does rhett syndrome occur genetically?
A mutation in the MeCP2 protein
How are globin genes regulated?
happens during fetal development
when is gene imprinting established?
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.
imprinting and prader-willi?
the maternal copy of the snrpn gene is imprinted
imprinting and angleman's
the paternal copy of the UBE3A gene is imprinted
what does the addition of the two drugs decitabine and 5-azacytidine cause and why?
They lead to hypomethylation because they cannot be methylation due to the N at position 5.
What is P15?
it is a tumor suppressor gene!
decitabine can be used to hypomethylate and prevent cancer formation when P15 is not working properly.
Children of IVF have a much greater risk of what disease?
Beckwith-Wiedemann syndrome (BWS)
How to detect BWS by lab techniques?
abnormal methylation will be seen
more cuts = less methylation
less cuts = more methylation
What environmental factors influence epigenetic changes?
1. site of fertilization
3. maternal care
4. diet (folate)