L10 - epigenetics

Question 1

what is the key to complexity of living organisms

Answer 1

complex regualtion

Question 2

what is epigenetics

Answer 2

regulation of gene expression independent of the dna sequence
is heritable

Question 3

what levle does epigenetics occur at

Answer 3

gene level - silence promoter by methylation etc
domain level - cluster of imprinted genes
chr level - heterochromatin

Question 4

what are some mechanisms of epigeneticcs

Answer 4

methulation
histone modification
non-coding rna

Question 5

describe the mol detail of methylation

Answer 5

conversion of cytosine to 5 methyl cytonsine
this is not stable mol
easaily chnage to thymidine
why most mut are c to t chnage

Question 6

where is methykation most likely to occur on dna

Answer 6

cpG island

short region of dna with high proportion og CG comp to rest of genome

Question 7

give eg of type of histone modification and the markers

Answer 7

acetylation - H3K9ac
phosphorylation -H3S10P
methylation - H3K9me

Question 8

what does histone modification do

Answer 8

defines strucutre

Question 9

what are non coding rna

Answer 9

functional rna that do not code pr
inc miRNA/ siRNA snoRNA
all interact

Question 10

how is miRNA processed and action

Answer 10

pre mi RNA processed by DROSA into hairpin
DICER complex tranforms into mature miRNA
RISC complex guides to dna
where can silence genes by binding to promoters etc

Question 11

what is imprinting

Answer 11

gene expr depenent on parent of origin

Question 12

how many genes in mammals found to show genomic imprinting

Answer 12

roughly 80

Question 13

descirbe the mosue experiment that shown genomic imprinting occurs

Answer 13

parthenogenic embryo (2x mat genome) - ovarian teratoma / disorg fetus/ no mbns
androgenic embryo (2x pat) vigorously grown mbn no embryo 

• ev that some gene only from one parent

Question 14

what central mech of genomic imprinting

Answer 14

methylation

Question 15

what is used to detect methylation of seq

Answer 15

sodium bisuldate
converts c to u
then amplify and seq
can detect if methy if c - methy if t - not mehty

Question 16

what parent of orgin is igf2 expr for

Answer 16

pat

if null = smaller

Question 17

how is igf2-h19 cluster diff in the parent of origin

Answer 17

in the paternal allele h19 is methy at the IC promoter region = therefore igf2 expr as CTCF cant bind
in the mat CTCF binds to IC where insulates and no Igf2 expr

Question 18

what diseases are assoc with the igf2-h19 locus

Answer 18

wilms tumour - failure of imprinting

beckwith-wiedemann syndrome - del of ic-biallelic expr of igf2

Question 19

what diseases linked to the deletion of proximal portion of chr 15 (15q11) a cluster with mutliple imprint genes

Answer 19

angelamann syndrome

prader willi syndrome

Question 20

what uniparentla disomy cause as and pws

Answer 20

2x mat - pws

2xpat - as

Question 21

what the clinical features of as and pws

Answer 21

as - slow dev/unusal movememtn/happy puppet

pws - ahort/obesity/immature phy dev

Question 22

how does uniparentla disomy occur

Answer 22

is the x2 chr from one parent
error in m2 disjucntion result in trisomy
then trisomy rescue remove extra chr and left with uniparental disomy

Question 23

what occurs to imprint when passed on to next gen

Answer 23

erase and restablished new parent sex specific impring in gamete/zygote

Question 24

why is x inact imp

Answer 24

compensate for gene dosage of male and female

Question 25

when does x inact occur

Answer 25

random at 15-16 days

Question 26

what does x inact lead to

Answer 26

mosaicism for functions coded bby heterosyg x link gene

eg calico cat

Question 27

what controls the choice of x for inact and initiates

Answer 27

xic (x inact centre)

Question 28

what is xist

Answer 28

x inact specific transcript
element of xic
initiates and propgates x inact
coats the x chr for inact 
no xist - no inact

Question 29

what is tsix

Answer 29

antisense xist

Question 30

what does x inact require

descirbe process

Answer 30

2x xic
xic changes xist rna form unstabel to highly expr
xist pot recruit factors to help make heterochromatin
tsix speculated role in x inact as at onset of x inact become monoallele expr is assoc with the active x until xist turned off

Question 31

what disease results from unbalandced x inact

Answer 31

duchene muscular dystrophy
fragile x
xaemophilia A

Question 32

what disease result of numerical x chr abn

Answer 32

klinefelter

turner