chapter 4

Question 1

what is a chromosome

Answer 1

genetic information onto one DNA molecule must be transferred + separated b4 division

more complex=less dense

Question 2

Eukaryote chromosome

Answer 2

linear

Question 3

Prokaryote chromosome

Answer 3

circular

Question 4

karyotype

Answer 4

DNA large loops and anchored

Question 5

what makes DNA into chromosomes?

Answer 5

packaging proteins
- condense DNA into smaller space and protect it

uses (+) histones to pack and bind bc phos backbone is (-)

Question 6

bacterial packaging

Answer 6

IHF binds to DNA and bends it and affects supercoiling

Question 7

Eukaryotic packaging

Answer 7

1. H3-H4- make DNA
2. H2A-H2B- make the octamer
3. octamer removed and (-) supercoiled DNA = easier sep now

Question 8

Histone tails

Answer 8

up to 25 AA

1. help compact DNA further
2. can be chemically modified

*some histone variants can be found at special chromatin

Question 9

What are the two histone modifications

Answer 9

Methylation: Lys & Arg rich, H3K4 activates

Acetylation: Lys residues
promote- Eu state (open)

Question 10

nucleosome formation

Answer 10

DNA is smoothly bent around histones but sharp in places (AT or CG)

minor groove at more AT rich

Question 11

Nucleosome remodelling

Answer 11

changed to allow proteins to access DNA

Question 12

ATP-dependent nucleosome remodeling complexes increase accessibility of DNA by

Answer 12

Sliding the histone octamer along the DNA

Removing the histone octamer and transferring it

Introducing loops into the DNA wrapped around a histone core

Question 13

chromatin packing

Answer 13

many layers of condense
10 nm nucleosomes w DNA
30 nm fiber nucleosomes together

Question 14

formation of 30 nm fiber

Answer 14

uses histone H1- binds to linker DNA in nucleosomes and helps compact

= further into loops of chromatin

Question 15

Euchromatin

Answer 15

decondense, stains light

Question 16

Heterochromatin

Answer 16

• more condense/dark stain
• has less recombination, which can protect RNA synthesis

Telomeres, centromeres, regions repetitive DNA sequences are heterochromatic

Question 17

chromosome packing (compare)

Answer 17

Prokaryotes:
circular, bent by IHF and DNA to nucleoid

Eukaryote:
linear, bent by histones and DNA into chromosomes
– more dense

Question 18

what do centromeres do

Answer 18

1. bind proteins to make kinetochore
2. attach microtubules from opposite spindles
3. pulls sisters apart (conserved)

Question 19

Point centromeres

Answer 19

small and defend seq

Question 20

Regional centromeres

Answer 20

larger, in fruit flies, plants and mammals

Question 21

holocentric chromosome

Answer 21

no defined centromere

Question 22

CENP-A

Answer 22

defined region where the nucleosomes have a histone H3 variant

where kinetochores assemble

Question 23

telomere

Answer 23

has both RNA and protein part
binding sites for protein
both stem and germline cells

Question 24

Simple tandem repeats

Answer 24

one C-rich strand and one G- rich strand

G-rich strand extends 5’-3’ *** causes most cancer!!!

limits cell division

Question 25

Three classes of telomere binding proteins

Answer 25

1. End-binding proteins the G rich overhang
2. Double-stranded binding proteins along the length
3. Other proteins that associate with the DNA binding proteins

Question 26

Non chromosomal: Pro

packing

Answer 26

• orgin @ ori
• 1 ori per chromosome
• sequence near ori finds the distribution of replicated chromosomes
• ter is termination
• yes rep problems

Question 27

Non chromosomal: Eu packing

Answer 27

• orgin @ ori
• many ori per chromosomes
• centromeres direct chromosome segregation
• telomeres stabilize ends

— no rep problems