Epigenetics

Question 1

epigenetics

Answer 1

• changes in gene expression not due to change in DNA sequence. due to modification of DNA and histones
• accounts for differentiated tissues and passing them on
• methylation silences, hypomethylation -> unregulated expression

Question 2

chromatin

Answer 2

• dynamic polymer that DNA winds around
• may be methylated, acetylated, ubiquitinated at different times and locations and opens/cloes to form heterochromatin and euchromatin to regulate gene expression

Question 3

ncRNA

Answer 3

-non-coding RNA. guides regions to make more compact chromatin. causes X activation and imprinting

X in activation: Xist RNA coats its own X chromosome to modify histones, inactivate x and form barr bodies. most of a one x is usually off

miRNA - short sequences bind complementary mRNA in 3’ untranslated region to control expression

• is inherited
• unregulated in many diseases like cancer

Question 4

Imprinting

Answer 4

-many genes often only need 1 allele turned on to function and other is turned off
-makes it important to get 1 chromosome from each parent, otherwise get 2x expression or none
(uniparental disomy)
-ICE = imprinted control elements - controls a region of clusterd imprinted genes
-gender matters; if father or mother turned off makes big difference:
1. female horse and male donkey -> mule
2. on 15q region: imprinting dad –> Prader Willi (mental retardation and obese)
imprinting mom–>Angelman syndrome -constant laughing

Question 5

Transgenerational epigenetics

Answer 5

• stress, diet and behavior can effect gene expression in children
• Royal Jelly in bees -> all bees matured into queens
• Folic Acid –> reduced Agouti expression and made mouse not obese and not yellow colored (brown instead)
• starved grandparents -> reduced lifespan in grandkids
• famine and war -> schizophrenia in kids
• cocaine –> demethylation in kids
• moms mood–> mental illness
• shock/smell association -> kids were sensitive

Question 6

epigenetics partial stability

Answer 6

• epigenetics modifications are rapid, lingering but not permanent unless environmental pressures persist, then they can adapt rapidly
• high mutation rate compared to DNA’s low mutation rate,which is necessary for passing on functional genome

Question 7

Epigenetics diseases

Answer 7

1. Rubenstein Taybi - broad thumbs, retardation
   - mutation in histone acetyltransferase
2. Rett syndrome - neurological disorder from mutation in DNA methyltransferase
3. Fragile X - 200+ CGG repeats causes methylation and inactivation of gene –> mental retardation. dicer recognizes RNA, turns it off and turns into heterchromatin
4. Cancer - from hypomethylation causeing unregulated gene expression OR tumor suppressors not being expressed (want durgs to inhibit methylation of these)