Exam 3: Epigenetics II Flashcards
differentiated adult cells can be reprogrammed to form
induced pluripotent stem cells (iPSCs)
epigenetic changes are associated with
cell differentiation
what makes the difference for each specialized cell type in a human organism
you begin life as a fertilized single cell which contains all the genetic information for you to turn into you. same set of nucleotide seq is in every cell in the body and what makes the difference for each specialized cell type is the way genes get turned on/off via epigenetic controlling mechanisms
in genomic imprinting, the expression of an allele depends on whether
it is inherited from the male or female parent
in mammals, the epigenetic program is reset to a
to a male or female pattern during gamete formation
what does it mean when parts of our genome are imprinted
different genetic behavior on the chromosome that came from your father compared to the one you got from your mother; alleles behave differently depending on which parent it came from
genomic imprinting is the epigenetic phenomenon by which
certain genes are expressed in a parent-of-origin-specific manner.
if the allele inherited from the father is imprinted =
methylated; it is silenced and only the allele from the mother is expressed ex
t/f: if u have a mutant allele, depending on who got it from, it can have a big or no impact at all
true
t/f: a chromosome region is differentially methylated depending on where you got it from (mom or dad)
true
genomic imprinting in male mammals
male mammals at the time of gamete formation establish a methylation pattern on various regions around the genome that represent male pattern. genes get turned off if highly methylated
genomic imprinting in female mammals
those same regions where males established a methylation pattern, those same regions are differentially methylated for females (some more or less depending on gene)
2/3 thirds of prader-willi syndrome and angelman syndrome occurs via
a deletion (3 mill bps); occurs near the centromere on chromosome 15 and bounded by a set of highly repeated sequences and are sticky. is thought that during meiosis, those regions stick together and leaves a loop that gets broken in a common 3 mill bp deletion
what is important about the region on chromosome 15 that gets deleted in prader-willi syndrome
region has multiple genes, several of which are only expressed by the father and one/two expressed by mother. those expressed by father is responsible for prader willi (SNRPN and snoRNAs deletion of genes)
how connected SNRPN and snoRNAs deletion to prader willi
shown to contribute (KO mouse study) the phenotype of prader willi
what is important about the region on chromosome 15 that gets deleted in angelman syndrome
region has multiple genes, several of which are only expressed by the father and one/two expressed by mother. if deletion comes from mother, the gene not expressed is UBE3A which codes for an enzyme that ubiquitinates many other genes (epigenetic modifier) that when not expressed gives you angelman syndrome
1/3 of prader willi syndrome and angelman syndrome occurs via
uniparental disomy (inheriting 2 copies of a chromosome from one parent); 2 from mom and none from dad
is uniparental disomy a deletion?
not a deletion, severe mutation in SNRPN (PWS) or UBE3A inactivation for angelman; functional alleles from dad is turned off in mom chromosomes thus no SNRPN expression and PWS
reasoning behind nondisjunction in a fertilized egg in uniparental disomy
nondisjunction event in mother during meiosis; 2 chromosome 15s get into egg bc of nondisjunction from mother and if fertilized there will be 3 chromosome 15s. this is not compatible with life, thus it is thought that another nondisjunction event eliminates 3 chromosome
