lecture 8

Question 1

humans have how many chromosomes

Answer 1

46

Question 2

humans have two copies of each chromosome, therefore they have

Answer 2

23

Question 3

the complex of DNA, histones and non-histone proteins with in the nucleus of a eukaryotic cell. the material of which chromosomes are made

Answer 3

chromatin

Question 4

one of the two copies of a replicated chromosome that is joined at the centromere to the other copy

Answer 4

chromatids

Question 5

two identical chromatids

Answer 5

sister chromatids

Question 6

center of sister chromatids that hold them together, where kinetochore forms

Answer 6

centromere

Question 7

prokaryotes have chromatin?

Answer 7

no, they have chromosomes that are “naked” no proteins bonded. Chromosomes live in spaghetti form

Question 8

three main things chromatin does

Answer 8

genome compaction
genome integrity
gene expression regulation

Question 9

explain genome compaction

Answer 9

allows genome to fit into nucleus

• twice around nucleosome
• wrapped around itself- 20 nm fibers (might not exist)
• rope
• wrapped rope
• chromsome

can be open, closed and remodeled
-chromatin remodeling enzymes

Histones acetylation (becomes less + charged) loosens its grip on DNA and DNA can be moved around

Question 10

explain genome integrity

Answer 10

protects genome from transposable elements (40% of genome) and DNA damage

when DNA is compacted bad things cant get in and TEs can’t react and cut itself out

Question 11

explain gene expression regulation

two types of chromosomes

Answer 11

heterochromatin

dark are silent. chromosome is binded up and does not allow transcription factors to attach

euchromatin
light is active. chromosome is unbinded and allows transcription factor to attach

Question 12

histone is made of

Answer 12

2 copies of H2A, H2B, H3 and H4

two copies of H3 and H4 bind to form H3-H4 tetramer

one copy of each H2A and H2B form a dimer
(happens twice)

H1 is a linker

Question 13

explain 3 ways chromatin remodeling enzymes can work

Answer 13

sliding
histone exchange
nucleosome eviction

Question 14

explain 3 ways chromatin remodeling enzymes can work

Answer 14

sliding
histone exchange
nucleosome eviction

Question 15

TEs

Answer 15

transposable elements

have matching ends, can cut itself out and then can paste back into genome somewhere else

if DNA is compacted, TEs can not interact with each other

Question 16

euchromatin

Answer 16

low nucleosomal density-
open
active transcription
light part of nucleus

Question 17

heterochromatin

Answer 17

high nucleosomal density
closed
non active- silent transcriptionally
dark part of nucleus

Question 18

histones tails

Answer 18

unfolded peptides that stick out

can have post translational modifications -(where acetylation occurs)
can activate or deactivate regions

Question 19

chromosomes like to stay in ___

Answer 19

discrete territories and with limited intermingling

Question 20

euchromatic regions like to be ___

Answer 20

close to the middle of the nucleus

Question 21

heterchromatic regions like to be ___

Answer 21

at border of nucleus

Question 22

explain DNA replication at the end. explain telomeres

Answer 22

DNA polymerase can only add to the 3’ has to go 5’ to 3’

RNA primers are added first and DNA polymerases extend the new strand after the primer

RNA primers are removed afterwards. DNA polymerase will fill in gaps where the primer was

at the end of the chromosome, primer is not added

therefore, at the end of DNA replication, 50-100 nucleotides are lost (BAD THING) too short=cell death

Question 23

telomerase

Answer 23

telomerase has an associated RNA that complements the 3’ overhang at the end of he chromosome

the RNA template is used to synthesize the complementary strand

telomerase is shifted and process is repeated

primase and DNA polymerase synthesize the complementary strand

active typically only in germ cells and stem cells

improper activation is contributor as how cancer replicates

Question 24

errors in telomerase

Answer 24

cancer- cells are replicated without shortening- can live forever!

Question 25

down syndrome

Answer 25

trisomy 21- XXY

two many chromosome

Question 26

deletion of one of two chromosomes

Answer 26

monosomy

Question 27

chromosomal duplication

Answer 27

polyploidy

Question 28

part of one arm of a chromosome is transferred to an arm or different chromsome

Answer 28

translocation

Question 29

example of translocation error

Answer 29

blood cancers

t(15;17)(q24;a21)- acute promyelocytic leukemia (APL)

Question 30

polyploidy and monosomy cause disease by generating

Answer 30

improper levels of gene expression

Question 31

translocations cause diseased by creating

Answer 31

improper proteins

Question 32

*** why does acetylation of histone N terminal tails correlate with high transcriptional activity?

Answer 32

acetylation neutralized the positive charge of the histone, decreasing the histones ionic interaction with the negative charge of DNA. This allows DNA to be exposed (TATA box, promoters) thus allowing transcription to occur

acetylation makes histone less +, loosens grip on -DNA, DNA can move/unbind and can be acted upon by transcription factors