Week 7_Epigenetics

Question 1

what are epigenetic modifications?

Answer 1

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

basically whether a gene is turned on or off

Question 2

epigenetic changes often change the ___

Answer 2

chromatin structure of a gene

Question 3

epigenetic modifications change how…

Answer 3

tightly DNA and histones bind to each other

Question 4

there are ___ types of chromatin

Answer 4

2

Question 5

what are the 2 types of chromatin?

Answer 5

euchromatin

heterochromatin

Question 6

describe euchromatin

Answer 6

DNA and histones are loosely associated

and

DNA is accessible to transcription factor/RNA polymerase binding

Question 7

describe heterochromatin

Answer 7

DNA and histones are tightly associated

and

DNA is not accessible to transcription factor/RNA polymerase binding

Question 8

what is chromatin remodeling?

Answer 8

changing the chromatin state

Question 9

how does chromatin remodeling occur?

Answer 9

thru histone acetylation

Question 10

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

Answer 10

acetylated

Question 11

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

Answer 11

amino terminal tails

Question 12

what is histone acetylation?

Answer 12

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

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

Question 13

histones are acetylated by ___

Answer 13

histone acetyl transferases (HATs)

Question 14

histones are deacetylated by ___

Answer 14

histone deacetylases (HDACs)

Question 15

what is hyperacetylation?

Answer 15

high levels of acetylation

histones are more ‘-‘ charged

Question 16

what is the result of hyperacetylation?

Answer 16

chromatin is more relaxed (DNA and histones wrap looser)

genes are more likely to be expressed

Question 17

relaxed chromatin genes are more likely to be ___

Answer 17

expressed

Question 18

what is DNA methylation?

Answer 18

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

Question 19

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

Answer 19

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

inhibits gene transcription

Question 20

cytosines are methylated by ___

Answer 20

DNA methyl transferases (DNMTs)

Question 21

cytosines are demethylated by ___

Answer 21

DNA demethyases

Question 22

are all cytosines methylated?

Answer 22

no

Question 23

which cytosines are methylated?

Answer 23

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

Question 24

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

Answer 24

CpG islands (C phosphodiester bonded to a G)

Question 25

CpG islands are often located in the...

Answer 25

promoter regions of genes

Question 26

what are epigenetic modifications?

Answer 26

changes in levels of: - histone acetylation - DNA methylation that occur at the same time combine to remodel chromatin and affect gene transcription

Question 27

what are the epigenetic modifications of euchromatin?

Answer 27

hyperacetylation of histones very little DNA methylation (promotes gene expression)

Question 28

what are the epigenetic modifications of heterochromatin?

Answer 28

hypoacetylation of histones high levels of DNA methylation (inhibits gene expression)

Question 29

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

Answer 29

differences in gene expression

Question 30

what is genome imprinting?

Answer 30

when methylation patterns are inherited by offspring

Question 31

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

Answer 31

promote maximum growth of the fetus

Question 32

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

Answer 32

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

Question 33

a balance in parental conflict theory results in...

Answer 33

fit offrspring allows mother to remain healthy and able to reproduce again

Question 34

an imbalance in parental conflict theory results in...

Answer 34

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

Question 35

more negative histones become...?

Answer 35

less attracted to DNA

Question 36

more negative histones --> DNA will become...?

Answer 36

more accessible to transcription factors

Question 37

more negative histones --> genes in that area of DNA are...?

Answer 37

more likely to be expressed

Question 38

what is hypoacetylation?

Answer 38

low levels of acetylation histones are more + charged

Question 39

what is the result of hypoacetylation?

Answer 39

closed chromatin (DNA and histones wrap more tightly) gene transcription is inhibited