Ch. 4 pt 1

Question 1

each DNA molecule that forms a linear chromosome must contain:

Answer 1

a centromere, two telomeres, and replication origins

Question 2

reproductive cycle of the cell

Answer 2

the orderly sequence by which a cell duplicates its chromosomes and other cell contents and then divides into two

Question 3

sister chromatids

Answer 3

tightly linked pair of chromosomes that arise from chromosome duplication during S phase.

they separate during M phase and move into different daughter cells

Question 4

centromere

Answer 4

constricted region of a mitotic chromosome that holds sister chromatids together

also the site on DNA where the kinetochore forms to capture microtubules from the mitotic spindle

Question 5

telomere

Answer 5

end of a chromosome, associated with characteristic DNA sequence that is replicated in a special way.

counteracts the tendency of the chromosome to shorten with each round of replication

Question 6

replication origin

Answer 6

a location on a DNA molecule at which duplication of the DNA begins by the formation of replication forks

Question 7

the DNA of ____ _______ is highly packed

Answer 7

mitotic chromosomes

Question 8

_____ chromosomes are mostly tightly packed, but have a dynamic structure.

Answer 8

interphase

Question 9

why do specific regions of interphase chromosomes decondense?

Answer 9

also access to specific DNA sequences for gene expression, DNA repair, and replication

Question 10

the packaging of DNA in chromosomes must allow…

Answer 10

rapid localized, on demand access to the DNA

Question 11

Euchromatin

Answer 11

region of an interphase chromosome that stains diffusely because it is NOT tightly packed

Question 12

heterochromatin

Answer 12

highly condensed even in interphase

generally transcriptionally inactive

Question 13

____ are a basic unit of eukaryotic chromosome structure

Answer 13

nucleosomes

Question 14

chromatin proteins may be divided into two classes:

Answer 14

histones
non histone chromosomal proteins

Question 15

the mass of histone proteins is…

Answer 15

about equal to the total mass of non-histone proteins

Question 16

histones

Answer 16

one of a group of small abundant proteins, rich in arginine and lysine (+ charged), that combine to form the nucleosome cores around which DNA is wrapped in eukaryotic DNA

Question 17

nucleosome

Answer 17

beadlike stucture in eukaryotic chromatin, composed of a short length of DNA rapped around an octameric core of histone proteins.

fundamental structural unit of chromatin

Question 18

structural organization of the nucleosome

histone octamer: two molecules each of…

Answer 18

H2A
H2B
H3
H4

Question 19

structural organization of the nucleosome

____ nucleotide pairs of DNA rap around the _______.

Answer 19

147
protein core (histone octamer)

Question 20

structural organization of the nucleosome

a nucleosome: ____ + _____

Answer 20

core particle + linker DNA

Question 21

structural organization of the nucleosome

a nucleosome includes an average of ____ nucleotide pairs

Answer 21

200

Question 22

structural organization of the nucleosome

in addition to main histone proteins…

Answer 22

there are specialized variant core histones

Question 23

each of the core histones has a largely unstructured _______ amino acid tail, which extends out from the DNA histone core. these histone tails are hot spots for different types of ___ ________ that control critical aspects of chromatin structure and function

Answer 23

N terminals

covalent modifications

Question 24

Histone H1:

Answer 24

linker histone protein that binds to DNA were it exits from a nucleosome and helps to compact nucleosomes

Question 25

nucleosomes have a ___ structure

Answer 25

dynamic

Question 26

chromatin remodelers

Answer 26

large, multi-protein complexes that use the energy of ATP hydrolysis to mobilize and restructure nucleosomes

Question 27

3 major functions of chromatin-remodeling complexes

Answer 27

1. reposition nucleosomes (nucleosome sliding) 2. eject histone octamers 3. exchange histones for variant core histones

Question 28

chromatin modifiers ___ modify histones

Answer 28

chemically

Question 29

chromatin remodeling complexes and chromatin modifiers...

Answer 29

influence chromatin structure and are important regulators of gene expression and cellular activities

Question 30

attractions between ___ compact the chromatin fiber

Answer 30

nucleosomes

Question 31

effect of chromatin structure on DNA function: _____ structure/packing histone ______ writer, reader, and eraser ____ spreading _____ modifications _____ and histone modifications ___________ have a special, inherited chromatin structure some forms of chromatin can be ____ ________

Answer 31

chromatin structure/packing histone modifications writer, reader, and ears proteins spreading chromatin modifications heterochromatin and histone modifications centromeres have a special, inherited chromatin structure some forms of chromatin can be directly inherited

Question 32

chromatin structure refers to

Answer 32

how tightly packed are the nucleosomes

Question 33

condensed :

Answer 33

inaccesible to transcription factors

Question 34

relaxed

Answer 34

transcription may be possible

Question 35

chromatin is now considered to be:

Answer 35

open and active or closed and inactive

Question 36

only about ___ % of the genome is packaged in that portion of the euchromatin associated with the actively expressed genes

Answer 36

20%