Chromatin

Question 1

Euchromatin

Answer 1

Decondensed, transcriptionally active form of chromatin

Question 2

Heterochromatin

Answer 2

Condensed, transcriptionally inactive form of chromatin

Question 3

Histone octamer

Answer 3

8 protein complex made up of two copies of histone proteins H2A, H2B, H3 and H4

Question 4

Nucleosome

Answer 4

basic repeating unit of eukaryotic chromatin, usually consisting of approximately 147bp DNA sequence wrapped around histone proteins

Question 5

147

Answer 5

147 bp of DNA to wrap twice around a nucleosome

Question 6

H1

Answer 6

linker histone that links nucleosomes

Question 7

Histone code

Answer 7

a hypothesis suggesting that DNA transcription is regulated by post translational modifications to histone proteins and tails

Question 8

What histone promotes condensation of DNA? (heterochromatin)

Answer 8

linker histone alters the path of DNA as it exits the nucleosome and this is believed to help it be more compact

Question 9

30nm fibre

Answer 9

helical formation of nucleosomes each composed of a particle wrapped by 147 bp DNA sequence and linked by a linker histone

Question 10

what charge are histone tails

Answer 10

positively charged

Question 11

Whya re histone tails positively charged?

Answer 11

they contain lots of basic residues (lysine and arginine)

Question 12

histone acetylation associated with

Answer 12

increase in gene expression

Question 13

Why does acetylation of histones decrease condensation of DNA? (promotes euchromatin)

Answer 13

Addition of acetyl groups to histone tails neutralises their positive charge and therefore decreases their attraction to the negative backbone of DNA, making DNA less compact

Question 14

What are the basic residues of histones?

Answer 14

K(lysine) and R(arginine)

Question 15

acetyl group

Answer 15

CH3CO

Question 16

Different combinations of histone marks result in

Answer 16

different condensation states

differential recruitment of other proteins

Question 17

H3K4me

Answer 17

trimethylation to 4th lysine of H3 histone

Question 18

Chromatin Accessibility Profile

Answer 18

just remember its a thing lol

Question 19

Three components of epigenetic inheritance

Answer 19

1. Histone code
2. RNA and protein made by parent cell
3. DNA methylation

Question 20

How does the cell epigenetically regulate DNA transcription?

Answer 20

moderates chromatin condensation state

Question 21

What are the two main states of chromatin?

Answer 21

heterochromatin (30nm fibre)

euchromatin (11nm fibre)

Question 22

Is histone code heritable?

Answer 22

Yes, it can be inherited by cells and even organisms

Question 23

DNA methylation

Answer 23

methylation of CpG islands which are typically located in or near gene promoters results in gene silencing

Question 24

enzyme that carries out DNA methylation

Answer 24

DNA methyltransferases