Chapter 5

Question 1

what is a nucleotide composed of?

Answer 1

a sugar-phosphate covalently linked to a base

Question 2

how are nucleotides linked?

Answer 2

covalently linked together into a polynucleotide chain, with sugar-phosphate backbone from which the bases extent

Question 3

what is a DNA molecule composed of?

Answer 3

2 polynucleotide chains (DNA strands)

Question 4

how are DNA strands held together?

Answer 4

by hydrogen bonds between paired bases

Question 5

how many h-bonds are formed between A & T?

Answer 5

2

Question 6

how many h-bonds are formed between G & C?

Answer 6

3

Question 7

how many rings do purines have?

Answer 7

2

Question 8

how many rings do pyrimidines have?

Answer 8

single

Question 9

what is a base pair?

Answer 9

purine-pyrimidine pair

Question 10

the 3’ end carries what?

Answer 10

an unlinked -OH group attached to 3’ position on sugar ring

Question 11

the 5’ end carries what?

Answer 11

a free phosphate group attached to 5’ position on sugar sing

Question 12

how many base pair per turn?

Answer 12

10

Question 13

what is chromatin?

Answer 13

combination of DNA and proteins that make up the contents of the nucleus of a cell

Question 14

what does chromosome painting do?

Answer 14

expose to a collection of fluorescent dye-labeled DNA

Question 15

what is a karyotype?

Answer 15

homologous chromosomes that are numbered and arranged in pairs

Question 16

what is inherited ataxia?

Answer 16

a disease that deteriorates motor skill

Question 17

what does ataxia do to chromosome 12?

Answer 17

one normal and one abnormal, longer with material from chromosome 4

Question 18

what strand encodes the information to make protein of RNA molecules?

Answer 18

coding strand, can be either strand

Question 19

in humans majority of chromosome don’t carry critical info

Answer 19

junk DNA

Question 20

what happens during interphase?

Answer 20

cell is actively expressing genes and DNA is replicated

Question 21

what happens during M phase?

Answer 21

chromosomes condense, gene expression ceases, and mitotic spindle forms from microtubules and other proteins.

Question 22

what is a nuclear envelope?

Answer 22

it forms around each chromosome set and the cell divides to produce 2 daughter cells in final step of M phase

Question 23

where are the multiple origins of replication on a chromosome?

Answer 23

1 centromere, and 2 telomeres

Question 24

during interphase, DNA replicates at the origin of replication in which direction?

Answer 24

bi-directionally from the origins across the chromosome

Question 25

what do telomeres contain? why?

Answer 25

repeated nucleotide sequences that enable the ends of chromosomes to be replicated, also cap the end.

Question 26

why do telomeres cap the end of chromosomes?

Answer 26

prevent it from being mistaken by the cell as broken DNA in need repair

Question 27

how is the nuclear envelope supported?

Answer 27

by the nuclear lamina

Question 28

what is the nuclear lamina?

Answer 28

network of protein filaments that form a thin layer underlying the inner nuclear membrane

Question 29

what is the chromatin that appears as a mass with dense chromosomal regions called?

Answer 29

heterochromatin (dark region)

Question 30

what is heterochromatin?

Answer 30

is chromatin expressing little to no genes, and located under the nuclear envelope

Question 31

what is the large dark region inside the nucleus?

Answer 31

nucleolus

Question 32

what does the nucleolus contain?

Answer 32

contain the genes fro ribosomal RNA

Question 33

where is rRNA located?

Answer 33

on multiple chromosome, but clustered together in the nucleolus

Question 34

what are the proteins on eukaryotic chromosomes?

Answer 34

histones nad nonhistone chromosome proteins

Question 35

nucleosomes contain DNA wrapped around a core of how many histone modules?

Answer 35

8

Question 36

how many histones make up the nucleosome core.

Answer 36

4 small proteins with high proportion of + charged amino acids

Question 37

how does the + charge help the nucleosome?

Answer 37

helps the histone bind tightly to the - charged sugar-phosphate backbone of DNA

Question 38

what pulls nucleosomes together into the 30-nm fiber?

Answer 38

a linker histone (H1)

Question 39

what does Histon H1 consist of?

Answer 39

a globular region plus a pair of long tails at its c-terminal and n-terminal ends

Question 40

what does the globular region do?

Answer 40

constrains an additional 20 base pairs of DNA where it exits from the nucleosome core.

Question 41

why is the globular region important?

Answer 41

for the formation of the 30 nm fiber

Question 42

what are the two ways chromatin structure differ with degrees of extension or condensation?

Answer 42

heterochromatin and euchromatin

Question 43

heterochromatin is more condensed than what?

Answer 43

euchromatin

Question 44

what does the chromatin-remodeling complex do?

Answer 44

repositions the DNA wrapped around the nucleosome

Question 45

how does the chromatin-remodeling complex work?

Answer 45

protein machine that uses the energy of ATP hydrolysis to change the position of DNA

Question 46

what happens when the tightly bound DNA moves along the complex?

Answer 46

loosen the underlying DNA, making it more accessible to other protein

Question 47

multiple rounds of nucleosome sliding does what?

Answer 47

decondense chromatin

Question 48

what can dictate how to stretch of chromatin is treated by the cells?

Answer 48

the pattern of modification of histone tails

Question 49

histones can be modified by the covalent attachment of a # of different chemical groups:

Answer 49

acetyl group, methyl group, phosphate

Question 50

where do most modifications go on the tail?

Answer 50

n-terminal tails of histone

Question 51

different combinations of histone tail modifications can confer what?

Answer 51

a specific meaning on the stretch of chromatin on which they occur

Question 52

heterochromatin-specific modifications allow what?

Answer 52

heterochromatin to form and spread

Question 53

what can repressive modifications to the histone tail do?

Answer 53

attract heterochromatin-specific proteins that reproduce the same modifications on neighboring proteins

Question 54

repressive modifications allow heterochromatin to spread until?

Answer 54

it encounters a DNA barrier sequence that prevents heterochromatin spread

Question 55

how can an expression of a gene be altered?

Answer 55

by moving it to another location in the genome

Question 56

what is the position effect?

Answer 56

activity of a gene depends on its position along a chromosome

Question 57

how can an X chromosome be inactivated?

Answer 57

by heterochromatin formation