10.1-10.10

Question 1

1st level of chromatin organization

Answer 1

involves nucleosomes, forms 10 nm fiber

Question 2

2nd level of chromatin organization

Answer 2

superhelical coiling of nucleosomes to generate 30 nm fiber

Question 3

3rd level of chromatin organization

Answer 3

looping of 30 nm fiber to generate 300 nm fiber
- involves interphase matrix proteins

Question 4

4th level of chromatin organization

Answer 4

for condensing chromosome during prophase
- 700 nm per sister chromatid
- 1400 for entire metaphase chromosome

Question 5

chromatin

Answer 5

dispersed chromosomes during interphase spread out in nucleus

Question 6

euchromatin

Answer 6

• lightly stained
• occupies most of nucleus
• less densely packed than mitotic chromosome

Question 7

heterochromatin

Answer 7

• darkly stained
• similar to chromosome at mitosis
• sometimes aggregate into chromocenter

Question 8

constitutive heterochromatin

Answer 8

regions that are always heterochromatic
- contain multiple copies of non-transcribed repeats
- low # of genes
- replicate late S phase
- genes translocated here likely inactivated

Question 9

facultative heterochromatin

Answer 9

euchromatin converted to heterochromatin

Question 10

events associated with causing condensation of euchromatin to heterochromatin

Answer 10

1. reduced acetylation of histones
2. increased methylation of histones
3. hypermethylation of cytosine bases in DNA

Question 11

Giemsa stain

Answer 11

used in staining process to generate G-bands

Question 12

do bands or interbands have a higher GC concentration

Answer 12

interbands

Question 13

are genes more concentrated in bands or interbands

Answer 13

interbands

Question 14

is p the short or long arm of a chromosome

Answer 14

short

Question 15

is q the short or long arm of a chromosome

Answer 15

long

Question 16

is GC-rich associated with coding or binding/structural

Answer 16

coding

Question 17

is AT-rich associated with coding or binding/structural

Answer 17

binding/structural

Question 18

where are telomeres and centromeres composed of

Answer 18

constitutive heterochromatin - 4th level of packing

Question 19

where is the 4th level of chromatin organization found

Answer 19

heterochromatin and mitotic chromosomes

Question 20

what is the DNA fiber arranged into

Answer 20

series of loops/domains attached to central proteinaceous matrix

Question 21

ethidium bromide

Answer 21

carcinogen stain that shows bands of DNA, intercalates between base pairs and generates positive superhelical turns
- enables researchers to see size of loops

Question 22

MARs (matrix) and SARs (scaffold)

Answer 22

DNA sites attached to proteinaceous structures in interphase nuclei

Question 23

what are the proteinaceous matrixes useful for

Answer 23

transcription and replication

Question 24

interphase matrix is associated with what level of packing?

Answer 24

3rd

Question 25

mitotic scaffold is associated with what level of packing?

Answer 25

4th

Question 26

are MARs fragments AT or GC rich

Answer 26

70% AT - attach to interphase matrix and mitotic scaffold

Question 27

prominent component of chromosome scaffold and mitotic nuclear matrix

Answer 27

topoisomerase II (and I)

Question 28

topoisomerase II

Answer 28

breaks 2 strands

Question 29

topoisomerase I

Answer 29

breaks 1 strand

Question 30

MTOC

Answer 30

microtubules organizing center that exists at poles of cell and on each chromosome at kinetochore

Question 31

what is good evidence that centromere is essential for segregation of chromosomes into progeny cells

Answer 31

loss of acentric fragments during mitosis/meiosis

Question 32

what is the kinetochore made of

Answer 32

centromeric-binding protein (attaches to centromere) and microtubule-binding protein (attaches to microtubules)

Question 33

when are cohesions made

Answer 33

G1

Question 34

when are cohesions added

Answer 34

S phase

Question 35

are centromeres or telomeres longer

Answer 35

centromeres

Question 36

any stretch of DNA capable of centromeric function (CEN) should confer what?

Answer 36

mitotic stability upon a plasmid

Question 37

centromeres are _____-rich

Answer 37

AT

Question 38

CEN sequences are essential for construction of what?

Answer 38

yeast and human artificial chromosomes

Question 39

where are tandem repeats usually found

Answer 39

centromeres and telomeres

Question 40

true or false: tandem repeats have coding function

Answer 40

false

Question 41

a satellite DNA

Answer 41

tandem arrays in primates (170 ntp)

Question 42

general formula for telomeric sequences

Answer 42

C(>1)A/T(1-4)

Question 43

human telomere repeating unit sequence

Answer 43

3'-CCCTAA-5'

Question 44

ssDNA G-tail of telomeres

Answer 44

14-16 nucleotides long on GT-rich strand

Question 45

telomerase

Answer 45

ribonucleoprotein enzyme that carries RNA template with same sequence as CA-rich strand to elongated GT-rich strand

Question 46

what type of activity does telomerase use

Answer 46

reverse transcriptase

Question 47

in which direction does telomerase work

Answer 47

synthesizes 5' to 3'

Question 48

why does yeast telomerase always need to be working

Answer 48

because it is one cell - loss of telomerase functions results in aging and death

Question 49

true or false: our telomerase gene is tcr silent, inducing aging

Answer 49

true

Question 50

true or false: telomerase is active in cancer cells

Answer 50

true

Question 51

how are the ends of chromosomes stabilized

Answer 51

forming long loop of DNA

Question 52

how is loop at end of chromosome made

Answer 52

3' ssDNA end displaces same sequence region upstream, ss region pairs with its homologous strand