lecture 14

Question 1

what bond holds the nucleotide subunits in a single DNA strand

Answer 1

phosphodiester

Question 2

what kind of bond holds the two DNA strands together (bases)

Answer 2

hydrogen

Question 3

during cell division, the nuclear material is organized into visible “threads” called

Answer 3

chromosomes

Question 4

chromatin =

Answer 4

DNA + histones

Question 5

nucleosome structure

Answer 5

histone proteins that DNA wraps around

Question 6

how long is human DNA

Answer 6

7 ft

Question 7

what is the packing ratio

Answer 7

10000:1 packing ratio

Question 8

whats the basic structural unit of a eukaryotic chromosome

Answer 8

nucleosome

Question 9

how many subunits in a histone

Answer 9

8 - it is an octamer

Question 10

how many times is DNA wrapped around a nucleosome

Answer 10

2

Question 11

are histone proteins basic or acidic

Answer 11

they are basic (positive charged aa arginine and lysine)

Question 12

what is DNAs charge?

Answer 12

it is negative which is why it can bind the histone core complex so well

Question 13

how many heterodimers in histone complex

Answer 13

4 histone heterodimers (4, 2 identical pairs)

Question 14

what are the heterodimers

Answer 14

(H2A, H2B, H3, H4) each x2

Question 15

what is histone H1

Answer 15

linker histone outside of wrapping to stabilize

Question 16

whats the histone structure

Answer 16

globular region of 3 a-helices
histone tail

Question 17

what groove of DNA faces the histone

Answer 17

minor groove

Question 18

does the diameter of chromosome packing increase as it gets more compacted

Answer 18

yes but its much shorter

Question 19

how are 30-nm chromatin fibre loops maintained

Answer 19

cohesion (cohesion ring)

Question 20

what is the 30-nm chromatin fibre structure

Answer 20

chromatin fibre gathered into a series of large supercoiled loops

Question 21

what are the 2 types of chromatin

Answer 21

euchromatin
heterochromatin

Question 22

what is euchromatin

Answer 22

loosely packed and easy to access chromatin (more likely to be involved in gene expression)

Question 23

what is heterochromatin

Answer 23

tightly packed chromatin that is hard to access

Question 24

what are the 2 types of heterochromatin

Answer 24

constitutive heterochromatin
facultative chromatin

Question 25

what is constitutive heterochromatin? examples?

Answer 25

it is always condensed (silent DNA) centromeres, telomeres, distal arm of Y chromosome

Question 26

what is facultative heterochromatin? examples?

Answer 26

inactive during certain portions or organisms life inactivated X chromosome (barr body)

Question 27

what is an inactive X chromosome (barr body) an example of

Answer 27

facultative heterochromatin

Question 28

what explains calico cats

Answer 28

facultative heterochromatin

Question 29

whats the histone code hypothesis

Answer 29

activity of chromatin region depends on degree of chemical modifications of histone tails

Question 30

what are the 3 forms of histone tail modifications that are seen

Answer 30

phosphorylation acetylation methylation

Question 31

what is the common site of amino acid modification on histones

Answer 31

N termini of H3 and H4 complex

Question 32

whats an initial step in the conversion of euchromatin to heterochromatin

Answer 32

removal of acetyl groups from H3/H4

Question 33

is a deacetylated histone more packed or less packed

Answer 33

more packed

Question 34

what is epigenetics

Answer 34

inheritance that is not encoded in DNA

Question 35

can an epigenetic state be reversed

Answer 35

yes

Question 36

what is transcription

Answer 36

process by which RNA is formed from a DNA template

Question 37

what is translation

Answer 37

process by which proteins are synthesized in the cytoplasm from an mRNA template

Question 38

whats the purpose of the messenger RNA (mRNA)

Answer 38

it is the intermediate molecule between a gene and a polypeptide