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BIOL 231 > Week 7_Epigenetics > Flashcards

Week 7_Epigenetics Flashcards

1
Q

what are epigenetic modifications?

A

modifications that change the expression of genes without changing the DNA sequence of the gene

basically whether a gene is turned on or off

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2
Q

epigenetic changes often change the ___

A

chromatin structure of a gene

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3
Q

epigenetic modifications change how…

A

tightly DNA and histones bind to each other

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4
Q

there are ___ types of chromatin

A

2

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5
Q

what are the 2 types of chromatin?

A

euchromatin

heterochromatin

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6
Q

describe euchromatin

A

DNA and histones are loosely associated

and

DNA is accessible to transcription factor/RNA polymerase binding

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7
Q

describe heterochromatin

A

DNA and histones are tightly associated

and

DNA is not accessible to transcription factor/RNA polymerase binding

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8
Q

what is chromatin remodeling?

A

changing the chromatin state

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9
Q

how does chromatin remodeling occur?

A

thru histone acetylation

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10
Q

the amino terminal tails of histone proteins extend out from the nucleosome core. They can be ___

A

acetylated

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11
Q

the ___ of histone proteins extend out from the nucleosome core. They can be acetylated.

A

amino terminal tails

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12
Q

what is histone acetylation?

A

negatively charged acetyl groups are attached to lysine in the N-terminal tails of histones

the added ‘-‘ charges make the histones more ‘-‘ charged

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13
Q

histones are acetylated by ___

A

histone acetyl transferases (HATs)

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14
Q

histones are deacetylated by ___

A

histone deacetylases (HDACs)

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15
Q

what is hyperacetylation?

A

high levels of acetylation

histones are more ‘-‘ charged

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16
Q

what is the result of hyperacetylation?

A

chromatin is more relaxed (DNA and histones wrap looser)

genes are more likely to be expressed

17
Q

relaxed chromatin genes are more likely to be ___

A

expressed

18
Q

what is DNA methylation?

A

when a methyl group can be added to cytosines in DNA to form 5-methylcytosine

19
Q

what is the signficance of the methyl group in DNA methylation?

A

the methyl group is a physical barrier to the binding of transcription factors

inhibits gene transcription

20
Q

cytosines are methylated by ___

A

DNA methyl transferases (DNMTs)

21
Q

cytosines are demethylated by ___

A

DNA demethyases

22
Q

are all cytosines methylated?

A

no

23
Q

which cytosines are methylated?

A

only the cytosines that are followed by a guanine (5’ CG 3’)

24
Q

many genes in the human genome have CG-rich regions of DNA sequence called ___

A

CpG islands (C phosphodiester bonded to a G)

25
Q

CpG islands are often located in the…

A

promoter regions of genes

26
Q

what are epigenetic modifications?

A

changes in levels of:
- histone acetylation
- DNA methylation

that occur at the same time

combine to remodel chromatin and affect gene transcription

27
Q

what are the epigenetic modifications of euchromatin?

A

hyperacetylation of histones

very little DNA methylation

(promotes gene expression)

28
Q

what are the epigenetic modifications of heterochromatin?

A

hypoacetylation of histones

high levels of DNA methylation

(inhibits gene expression)

29
Q

different cell types have different methylation/acetylation patterns which contribute to…

A

differences in gene expression

30
Q

what is genome imprinting?

A

when methylation patterns are inherited by offspring

31
Q

in the sperm, the paternal methylation pattern favors the expression of genes that will…

A

promote maximum growth of the fetus

32
Q

in the egg, the maternal methylation pattern favors the expression of genes meant to…

A

push back against the paternal genes and promote modest growth of the fetus

33
Q

a balance in parental conflict theory results in…

A

fit offrspring

allows mother to remain healthy and able to reproduce again

34
Q

an imbalance in parental conflict theory results in…

A

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

35
Q

more negative histones become…?

A

less attracted to DNA

36
Q

more negative histones –> DNA will become…?

A

more accessible to transcription factors

37
Q

more negative histones –> genes in that area of DNA are…?

A

more likely to be expressed

38
Q

what is hypoacetylation?

A

low levels of acetylation

histones are more + charged

39
Q

what is the result of hypoacetylation?

A

closed chromatin (DNA and histones wrap more tightly)

gene transcription is inhibited

BIOL 231 (23 decks)

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