L10 - epigenetics Flashcards Preview

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Flashcards in L10 - epigenetics Deck (32):
1

what is the key to complexity of living organisms

complex regualtion

2

what is epigenetics

regulation of gene expression independent of the dna sequence
is heritable

3

what levle does epigenetics occur at

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

4

what are some mechanisms of epigeneticcs

methulation
histone modification
non-coding rna

5

describe the mol detail of methylation

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

6

where is methykation most likely to occur on dna

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

7

give eg of type of histone modification and the markers

acetylation - H3K9ac
phosphorylation -H3S10P
methylation - H3K9me

8

what does histone modification do

defines strucutre

9

what are non coding rna

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

10

how is miRNA processed and action

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

11

what is imprinting

gene expr depenent on parent of origin

12

how many genes in mammals found to show genomic imprinting

roughly 80

13

descirbe the mosue experiment that shown genomic imprinting occurs

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

14

what central mech of genomic imprinting

methylation

15

what is used to detect methylation of seq

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

16

what parent of orgin is igf2 expr for

pat
if null = smaller

17

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

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

18

what diseases are assoc with the igf2-h19 locus

wilms tumour - failure of imprinting
beckwith-wiedemann syndrome - del of ic-biallelic expr of igf2

19

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

angelamann syndrome
prader willi syndrome

20

what uniparentla disomy cause as and pws

2x mat - pws
2xpat - as

21

what the clinical features of as and pws

as - slow dev/unusal movememtn/happy puppet
pws - ahort/obesity/immature phy dev

22

how does uniparentla disomy occur

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

23

what occurs to imprint when passed on to next gen

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

24

why is x inact imp

compensate for gene dosage of male and female

25

when does x inact occur

random at 15-16 days

26

what does x inact lead to

mosaicism for functions coded bby heterosyg x link gene
eg calico cat

27

what controls the choice of x for inact and initiates

xic (x inact centre)

28

what is xist

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

29

what is tsix

antisense xist

30

what does x inact require
descirbe process

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

31

what disease results from unbalandced x inact

duchene muscular dystrophy
fragile x
xaemophilia A

32

what disease result of numerical x chr abn

klinefelter
turner