Exam 2: Chromatin and Chromosomes Flashcards Preview

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Flashcards in Exam 2: Chromatin and Chromosomes Deck (29)
1

in interphase, DNA is...

decondensed and coiled around protein spools

2

nucleosome "beads on a string"

protein spool that DNA of eukaryote chromosomes are always spooled around

left handed spiral

eukaryotes only

3

nucleosome core

roundish disk made of 8 histones

150 base pairs of dsDNA in 2 loops

allows chromosomes to be condensed in length

4

what proteins are nucleosomes made of

histones (100-200 AAs)

25% lysine and arginine to help bind to acidic phosphates on DNA

5

each core is wrapped in ____ turns of DNA

~1.7, almost 2

6

between nucleosomes there is additional ____

unspooled linker DNA

this all forms a repeating unit of roughly 200 bp

150 bp nucleosome DNA and 50 bp linker DNA

7

each nucleosome core is an ____

octamer

8 histone molecules

8

if you mix histones together...

they will spontaneously assemble into nucleosome cored

9

if you mix DNA with nucleosome cores...

the DNA naturally coils around the cores

10

what happens during s-phase

a ton of nucleosome cores are made

newly replicated DNA wraps around immediately

11

nucleosomes shorten DNA by a factor of _

7; 3 feet to 5 inches

the nucleosome packing shortens DNA by another 7

total packing is by a factor of 49/50

12

nucleosomes don't only stick to DNA...

they stick to each other making disk-like structures

a strand about 30nm called chromatin fiber (next level of supercoiling) involving histone tails

13

scaffold proteins and loops

central core of skeleton for the chromosome

chromatin fibers form loops and are attached to the scaffold

loops exist in interphase and metaphase chromosomes

14

matrix associated region

AT-rich regions of DNA attached to scaffold protein

attach bases of DNA loops

MAR=SAR (scaffold associated region)

15

the final shortening of chromosomes occurs during _____

prophase

highest level of chromatin packing

16

how do we number the human karyotype

number the autosomes from longest to shortest

divide into groups A-G based on shapes

sex chromosomes are simply X and Y

17

what is the smallest chromosome

chromosome 21

it's out of order~

18

most chromosomes have regions of....

constitutive heterochromatin near the centromeres

large heterochromatic centromeric bands on 1, 9, 16

19

acrocentric autosomes include...

13, 14, 15, 21, 22

all have ribosomal genes on the short arms

20

chromatin contains

both DNA and protein

more protein than DNA

21

nonhistone proteins in chromatin include both

structural and regulatory proteins

22

differences between euchromatin and heterochromatin

the amount of packing

23

heterochromatin

more condense, less active, late-replicating, dark staining

constitutive is always hetero

facultative is sometimes hetero

24

euchromatin

decondensed and active

facultative is sometimes euchromatin

25

constitutive heterochromatin

always hetero

tails of Y's, all centromeric regions

especially 1, 9, 16

26

facultative heterochromatin

goes between hetero and euch

barr body

female's x chromosome

27

Giemsa stain

G-bands are alternating light and dark bands on chromosomes when a staining technique is used

bands are large and contain many genes

numbered to ID regions, blocks of genes, deletions

tell chromosomes apart

28

with careful banding techniques...

recognize same chromosome in diff generations

this is b/c some parts of chromosomes are more variable, esp in heterochromatic regions

29

if you remove histones from a mitotic chromosome what fraction of the original weight of the chromosome does this remove?

50%

1/3 remaining mass is other proteins including scaffolds

resulting structure is loose, relaxed DNA still attached in large loops to the scaffold