Lecture 15 - Chromosome structure and genome organization - part 1

Question 1

Each base pair of B-DNA contributes about _______Angstroms to its length

Answer 1

3.4

Question 2

The 23 chromosomes of the 3 billion bp human genome have a length of about

Answer 2

1 meter

Question 3

Each chromosome is a complex of

Answer 3

linear duplex DNA and protein

Question 4

Chromosomes assume their most condensed forms only during

Answer 4

metaphase, the stage of the cell cycle when the chromosomes align on the mitotic spindle

Question 5

Chromatin

Answer 5

A cells DNA with all associated proteins

Question 6

Eukaryotic DNA is tightly bound to

Answer 6

histones

Question 7

What constitutes half the mass of a eukaryotic chromosome?

Answer 7

histones

Question 8

Chromatin serves to

Answer 8

compact and organize eukaryotic DNA

Question 9

Chromatin greatly influences

Answer 9

gene regulation

Question 10

Chromatin is made up of repeating units called

Answer 10

nucleosomes

Question 11

What four histone proteins are associated with DNA

Answer 11

H2A, H2B, H3, and H4

Question 12

H1 is associated with

Answer 12

the nucleosome

Question 13

Histones have strong _______ properties

Answer 13

basic

Question 14

In histones, 25% of the amino acids are either

Answer 14

arginine or lysine

Question 15

Histones have positively charged amino acids that can

Answer 15

interact strongly with negatively charged DNA which stabilizes the core nucleosome

Question 16

Histone (H1) further stabilizes the complex by binding to the

Answer 16

linker DNA

Question 17

Histones bind exclusively to

Answer 17

the inner face of DNA

Question 18

Micrococcal nuclease degrades

Answer 18

chromatin to single nucleosomes

Question 19

The DNA superhelix has a radius of

Answer 19

42 Angstroms

Question 20

The DNA superhelix has a pitch (rises per turn) of

Answer 20

26 Angstroms

Question 21

Does DNA follow a uniform superhelical path?

Answer 21

No

Question 22

The left-handed wrapping of DNA around the histone octamer stores

Answer 22

negative supercoils

Question 23

If the DNA in a nucleosome is straightened out, the DNA will be

Answer 23

underwound

Question 24

Underwinding is what is needed to

Answer 24

separate the two DNA strands during replication and transcription

Question 25

30 nm Chromatin fiber has how many nucelosomes?

Answer 25

12

Question 26

In 30 nm Chromatin, the nucleosomes follow a zigzag path such that

Answer 26

all odd-numbered nucleosomes form a stack as do all even-numbered nucleosomes

Question 27

1 Angstrom is about ______ nm?

Answer 27

10

Question 28

30 nm Chromatin fiber has two stacks of nucleosomes winding around each other in

Answer 28

two left-handed helices

Question 29

30 nm Chromatin fiber has how many nucleosomes per turn?

Answer 29

28

Question 30

DNA in assembly with chromatin fiber is compacted by approximately _____ fold

Answer 30

36

Question 31

Naturally occurring chromatin has more

Answer 31

irregularly spaced nucleosomes

Question 32

The 30 nm fiber in chromatin is stabilized by interactions involving

Answer 32

H2A-H2B dimers and histone H4

Question 33

H4’s positively charged N-terminal tail can bind to a negatively charged region on an exposed face of the

Answer 33

H2A-H2B dimer in a neighboring nucleosome

Question 34

Acetylation of H4’s N-terminal tail reduces its

Answer 34

positive charge

Question 35

Each histone has a ______ tail that extends out from the core structure

Answer 35

amino-terminal

Question 36

Histone tails contain a number of _________ residues

Answer 36

lysine and arginine

Question 37

Covalent modifications of the histone tails play an important role in

Answer 37

regulating gene expression via chromatin modeling

Question 38

HAT stands for

Answer 38

Histone acetyltransferase

Question 39

HAD stands for

Answer 39

Histone deacetylase

Question 40

Chromatin structure plays a major role in controlling

Answer 40

eukaryotic gene expression

Question 41

In eukaryotic gene expression, highly compact chromatin contains genes that are

Answer 41

turned off

Question 42

In eukaryotic gene expression, less compact chromatin contains genes that are

Answer 42

turned on

Question 43

Euchromatin

Answer 43

Loosely packed chromatin

Question 44

Heterochromatin

Answer 44

Densely packed chromatin

Question 45

In chromatin loops, loops of DNA are attached to a

Answer 45

protein scaffold

Question 46

In chromatin loops, the loops enter and exit the scaffold at

Answer 46

nearly the same point

Question 47

Matrix-attachment regions (MARs), also known as Scaffold-attachment regions (SARs) are

Answer 47

DNA sequences interspersed in the genome

Question 48

MARs anchor to the nuclear matrix, forming

Answer 48

radial loops

Question 49

In chromatin loops, each loop forms a closed circle by the attachment of its base to

Answer 49

the protein scaffold and thereby maintains its negative supercoiling

Question 50

Nonhistone proteins constitute about ______ % of chromosomal proteins

Answer 50

10

Question 51

Nonhistone proteins participate in

Answer 51

organizing the DNA in higher-order structure