Final: Epigenetic Inheritance Flashcards
adult cells are highly _____
differentiated states with specific genes turned on or off
when an adult cell divides…
it passes on the status of every gene to daughter cells
5 aspects of gene regulation passed on
histone variants and modifications
DNA modifications (methylation of cytosines)
chromatin binding proteins (TFs)
chromatin structural RNA
genetic inheritance
a dividing cell passes on its genes to daughter cells
this means the DNA sequence only
epigenetic inheritance
a dividing cell also passes on the regulatory status of each gene
all regulatory mechanisms are passed on to daughter cells
what is a barr body an example of
epigenetic inheritance
barr body replicates and is passed on, then turns into a barr body again
how do daughter cells stay the same as parent cells?
the genes “remember” what they were doing before
so they keep doing it in the daughter cells
epigenetic inheritance
4 things the daughter cells end up having
same histone modifications
same cytosine methylations
same bound TFs
same bound regulatory RNA
2 pathways to epigenetic inheritance
from cell to cell within a body
from parent to offspring between generations
genomic imprinting
parent-to-child epigenetic inheritance
causes the same allele to have different effects
effect depends on the sex of the parent transmitting the allele
same gene can be “pre-methylated” two different ways in eggs or sperm
DMR
differently methylated region
regions of DNA that are methylated one way in eggs and another way in sperm
genomic imprinting occurs in the ____
germline
offspring grows up keeping the methylation pattern of parents
parental imprinting is erased in germline of offspring
then the genes are re-imprinted according to the offspring’s own sex
CpG island
genomic imprinting in mammals involves methylation of CpG islands
there may be additional mechanisms for epigenetic inheritance in gametes
IGF2
protein hormone that promotes fetal growth
mother’s copy is shut down by methylation
father’s copy does all the work
it doesn’t matter if the mother’s copy gets mutated
if father’s copy is mutated then you don’t grow right
Beckwith Wiedemann Syndrome
same genes are in mice chromosome 7 and human 11
loss of mother’s copy causes BW syndrome
paternal homolog already shut down
Prader Willi Syndrome and Angelman Syndrome
2 genetic diseases coming from 1 genetic region
PW leads to extreme appetite and obesity
Angelman leads to hyperactivity
to be normal, inherit one imprinted copy of DMR from each parent
how get Prader Willi
inherit only mothers DMR
how get Angelman
inherit only fathers DMR
causes of Prader Willi
paternal deletion
paternal methylation defect
maternal uniparental disomy (2 copies of maternal #15)
causes of Angelman
maternal deletion
maternal methylation defect
paternal uniparental disomy (2 copies of paternal #15)
uniparental disomy
a person has normal diploid # of chromosomes (46)
but for one pair of homologs, both copies came from just 1 of the parents
how does uniparental disomy occur
trisomic zygote sorts into disomy in early division of embryo
disomic gamete could meat a nullisomic gamete
monosomic zygote duplicates in early division
DMRs
to be normal you need:
one haploid set of male imprinted chromosomes
one haploid set of female imprinted chromosomes
all mammals use genomic imprinting but not on all ____
genes
most genes are not in ___, so these problems dont arise with them
DMRs
can environmental factors negatively affect genomic imprinting?
yes: in vitro fertilization multiplies rate of BW syndrome 3-4x
also: exposing pregnant rats to fungicide Vinclozolin causes epigenetic effects
passed on several generations but only in males
