Epigenetics

Question 1

Methylation

Answer 1

98% of genome at a time
Tells not to trx
Promoter region is less methylated then other regions 1cpg island/10bps vs 1 CpG for 100bps

Question 2

CpG islands

Answer 2

TSS of housekeeping genes

Question 3

Imprinting

Answer 3

Father/Mother give their methylated/unmethylated genes directly to child, then lose methylation until baby, then high methylation again
Imprinted genes expressed preferentially from one allele
-the expressed gene is not methylated

Question 4

How to add/get rid of methyl

Answer 4

Methyl writers/erasers
DNMT/DMTase
Sometimes replicated cells are not methylated-use de novo DNMT addition

Question 5

Methyl group functionality

Answer 5

Can have trx factors bind (function as promoter/inhibitor)

Question 6

Rett Syndrome

Answer 6

X linked dominant, dev normally for 6-18 months, apraxia, breathing abnormalities
Results because missing methyl CpG binding protein MECP2-increase trx of genes that should be off
Boys die after birth because only 1 X chrome-more fatal

Question 7

MECP2

Answer 7

inhibits trx, no binding to methylated CpG island, large amount in neurons

Question 8

Methylation pattern

Answer 8

Similar when twins are born, very different as get older, each tissue of body has different amounts of methylation

Question 9

Post translational Mod of Histones (4 types)

Answer 9

Covalent bonds,
Reversibly modified
Tell if chromatin  relaxed or not
Acetylation of lysine-relax
Phosphorylation of serine
Methylation of lysine-condense
Sumoylation

Question 10

HDAC

Answer 10

histidine deacytylases
used in cancer
small molecules that compact histones by removing acetylene

Question 11

histone writers

Answer 11

methyltransferases and HATs/Kinases

Question 12

histone erasers

Answer 12

HDACs and demethylases

Question 13

Euchromatin histone mods

Answer 13

acetylation up, methylation down, H3-K4 is methylated

Question 14

Heterochromatin histone mods

Answer 14

low acetylation, high methaltion, H3-K9 methylated

Question 15

Bar bodies

Answer 15

Inactivated X chromasome, calico cat

Question 16

X-inactivation Center

Answer 16

Both Xist and Tsix produce noncoding mRNA transcripts
Tsix antisense to Xist so can bind
Before inactivation Xist expressed at low concentrations in both chromosomes
Shortly after 1 chrom begins to express Tsix in high levels, inhibits Xist
This is active X chromosome
Chromosomes are really close together-kiss exchange factors and this results in 1 expressing more Tsix

Question 17

Xist inactivation

Answer 17

Starts from one point, radiates outward, recruits histones H3 and H4 for hypoacetylation

Question 18

Phenotypical plasticity

Answer 18

Can have multiple phenotypes with one genotype-arise from organism to respond to environment or as modification of developmental events (sustained neuronal activity, drugs, mood disorders)

Question 19

Hongerwinter

Answer 19

No food, many diseases, small and short in stature kids, have problems that follow them throughout life
Hypomethylation in IGF2-gene that is maternally imprinted-kids of hongerwinter children (mothers only) had kids with same long term problems

Question 20

IGF-2 gene

Answer 20

Maternally imprinted has differential methyl region-result in 1 gene have balletic expression

Question 21

Agouti gene

Answer 21

Has variable methylated region
mRNA made during development and silenced rest of life
Unsilenced=yellow and diabetes problems
These mice are genetically identical

Question 22

Follate (b6) and Choline (b12)

Answer 22

Methyl supplementors
Used in Ag mouse-no agouti symptoms
Ag gene methylated

Question 23

Bisulfite Conversion

Answer 23

Bisulfite converts C to U if C is unmethylated

U can be in DNA-becomesT in when replicated

Question 24

Methyl Sensitive enzymes

Answer 24

Useful for determining methylation pattern

Cancer to normal has different methylation pattern