Week 7_Epigenetics Flashcards
what are epigenetic modifications?
modifications that change the expression of genes without changing the DNA sequence of the gene
basically whether a gene is turned on or off
epigenetic changes often change the ___
chromatin structure of a gene
epigenetic modifications change how…
tightly DNA and histones bind to each other
there are ___ types of chromatin
2
what are the 2 types of chromatin?
euchromatin
heterochromatin
describe euchromatin
DNA and histones are loosely associated
and
DNA is accessible to transcription factor/RNA polymerase binding
describe heterochromatin
DNA and histones are tightly associated
and
DNA is not accessible to transcription factor/RNA polymerase binding
what is chromatin remodeling?
changing the chromatin state
how does chromatin remodeling occur?
thru histone acetylation
the amino terminal tails of histone proteins extend out from the nucleosome core. They can be ___
acetylated
the ___ of histone proteins extend out from the nucleosome core. They can be acetylated.
amino terminal tails
what is histone acetylation?
negatively charged acetyl groups are attached to lysine in the N-terminal tails of histones
the added ‘-‘ charges make the histones more ‘-‘ charged
histones are acetylated by ___
histone acetyl transferases (HATs)
histones are deacetylated by ___
histone deacetylases (HDACs)
what is hyperacetylation?
high levels of acetylation
histones are more ‘-‘ charged
what is the result of hyperacetylation?
chromatin is more relaxed (DNA and histones wrap looser)
genes are more likely to be expressed
relaxed chromatin genes are more likely to be ___
expressed
what is DNA methylation?
when a methyl group can be added to cytosines in DNA to form 5-methylcytosine
what is the signficance of the methyl group in DNA methylation?
the methyl group is a physical barrier to the binding of transcription factors
inhibits gene transcription
cytosines are methylated by ___
DNA methyl transferases (DNMTs)
cytosines are demethylated by ___
DNA demethyases
are all cytosines methylated?
no
which cytosines are methylated?
only the cytosines that are followed by a guanine (5’ CG 3’)
many genes in the human genome have CG-rich regions of DNA sequence called ___
CpG islands (C phosphodiester bonded to a G)
CpG islands are often located in the…
promoter regions of genes
what are epigenetic modifications?
changes in levels of:
- histone acetylation
- DNA methylation
that occur at the same time
combine to remodel chromatin and affect gene transcription
what are the epigenetic modifications of euchromatin?
hyperacetylation of histones
very little DNA methylation
(promotes gene expression)
what are the epigenetic modifications of heterochromatin?
hypoacetylation of histones
high levels of DNA methylation
(inhibits gene expression)
different cell types have different methylation/acetylation patterns which contribute to…
differences in gene expression
what is genome imprinting?
when methylation patterns are inherited by offspring
in the sperm, the paternal methylation pattern favors the expression of genes that will…
promote maximum growth of the fetus
in the egg, the maternal methylation pattern favors the expression of genes meant to…
push back against the paternal genes and promote modest growth of the fetus
a balance in parental conflict theory results in…
fit offrspring
allows mother to remain healthy and able to reproduce again
an imbalance in parental conflict theory results in…
offspring that are too small or unfit to survive
or
offspring that grows so large and use so many maternal resources that it ends up hurting or killing the mother or leaves her unable to reproduce again
more negative histones become…?
less attracted to DNA
more negative histones –> DNA will become…?
more accessible to transcription factors
more negative histones –> genes in that area of DNA are…?
more likely to be expressed
what is hypoacetylation?
low levels of acetylation
histones are more + charged
what is the result of hypoacetylation?
closed chromatin (DNA and histones wrap more tightly)
gene transcription is inhibited
