chapter 5

Question 1

what was griffith’s contribution

Answer 1

demonstrated that cells carry a “transforming” molecule

Question 2

what was avery, mcleod, mccarty’s constribution

Answer 2

demonstrated that DNA is the genetic material

Question 3

what was watson and crick’s contribution

Answer 3

double-helix model of DNA
-two strands of DNA are antiparallel and the bases are stacked on one another
-two strands connected by A-T and G-C with 10 base pairs per helix turn

Question 4

what are the four basic molecular genetic processes

Answer 4

1. transcription
2. RNA processing
3. mRNA translation
4. replication

Question 5

what is the difference in structure in ribose and deoxyribose

Answer 5

in the 2’ position, ribose has an OH

in the 2’ position, deoxyribose has just an H

Question 6

purines

Answer 6

A+G
2 rings

Question 7

prymidines

Answer 7

U+T+C
one ring

Question 8

what is at the 5’ end of a DNA molecular

Answer 8

phosphate group

Question 9

what is at the 3’ end of a DNA molecule

Answer 9

OH group

Question 10

what are the building blocks of a nucleotide

Answer 10

phosphate, sugar, base

Question 11

what connects nucleotides in a DNA molecule

Answer 11

H bond

Question 12

how can protein interaction bend DNA

Answer 12

the conserved C-terminal domain of the TATA box-binding protein (TBP) binds to the minor groove of specific DNA sequences rich in A and T, untwisting and sharply bending the double helix

Question 13

how can the G+C content of DNA affect the melting temperature

Answer 13

the temp at which DNA denatures increases with the proportion of G+C base pairs

the Tm is a function of the G·C content of the DNA; the higher the G+C percentage, the greater the Tm

Question 14

what does topoisomerase I do

Answer 14

1. relieves torsional stress on DNA
2. associates with parental DNA strand ahead of the large T-antigen

Question 15

what did meselson-stahl contribute

Answer 15

the idea that DNA replication is semiconservative

Question 16

what direction is DNA synthesized

Answer 16

5’—->3’

Question 17

what are the three requirements for DNA synthesis

Answer 17

1. a primer strand with a free 3’ terminus
2. a template strand that is base-paired to the primer
3. a source of dNTPs

Question 18

what is DNA polymerase’s job in DNA synthesis

Answer 18

DNA polymerase catalyzes formation of a phosphodiester bond between the 3’ oxygen of the primer stand and the alpha phosphate of a correctly base-paired dNTP

Question 19

what does DNA polymerase I do

Answer 19

catalyzed the reaction that adds a single nucleotide to the growing complement strand

Question 20

when a nucleotide is added, what happens

Answer 20

two terminal phosphates are cleaved off, released as pyrophosphate

Question 21

what are the general properties of DNA polymerases

Answer 21

1. depend on a single stranded nucleotide
2. can add free nucleotides ONLY to the 3’ - OH end of an EXISTING polynucleotide (DNA or RNA)
3. direction of synthesis is 5’ to 3’

Question 22

where does DNA synthesis begin in a bacterial chromosome

Answer 22

a site termed the origin of replication

Question 23

how does DNA synthesis proceed in a bacterial chromosome

Answer 23

bidirectionally (this results in 2 replication forks)

note: the replication forks eventually meet at the opposite side of the bacterial chromosome, ending its replication

Question 24

how is eukaryotic DNA synthesis different than prokaryotic

Answer 24

1. there is more DNA
2. the chromosomes are linear
3. the DNA is complexed with proteins
4. eukaryotic chromosomes contain multiple origins of replication allowing the genome to be replicated in a few hours

Question 25

what enzyme does proofreading

Answer 25

DNA polymerases note: ALL DNA polymerases have 3' to 5' exonuclease activity that allows for proofreading

Question 26

what does helicase (viral large T antigen) do

Answer 26

unwinds the parental DNA strands, beginning at a replication origin

Question 27

what does DNA polymerase ε (Pol ε) (epsilon) do

Answer 27

extends the LEADING strand up to the replication fork

Question 28

what does PCNA do

Answer 28

-sliding clamp keeps Pol ε stable and associated with the replication fork forms complexes with DNA Pol ε and Pol δ, preventing dissociation from the DNA template

Question 29

what does RPA do

Answer 29

multiple copies of RPA bind the lagging strand (and leading) by keeping it stable and orienting it in the optimal position for replication by Pol δ binds to single-stranded DNA that has been unwound maintains ssDNA (single-stranded DNA) template for copying by DNA polymerases

Question 30

what does primase RNA polymerase-DNA polymerase α (Pol α) complex do

Answer 30

synthesizes primers for LAGGING STRAND synthesis

Question 31

helicase is what kind of molecule

Answer 31

hexamer (6 identical subunits)

Question 32

PCNA–Pol δ complex does what

Answer 32

binds the 3' end of each primer and extends the primer to synthesize most of an okazaki fragment

Question 33

what shape is PCNA

Answer 33

donut! double-stranded DNA passes through the hole in the center

Question 34

what is RFC and what does it do

Answer 34

"clamp loader" binds to PCNA before the "clamp" is opened and opens the ring so that it can encircle a short region of DNA synthesized by Pol α

Question 35

what does the Pol delta RFC PCNA complex do

Answer 35

displaces the primase-Pol alpha complex following primer synthesis

Question 36

DNA polymerase alpha is the only polymerase to

Answer 36

associate with primase

Question 37

what does DNA polymerase alpha/primase complex do

Answer 37

synthesizes a short RNA/DNA hybrid -10 RNA nucleotides followed by 20 to 30 DNA nucleotides

Question 38

what is the primer synthesized by Pol alpha-primase used for

Answer 38

used by DNA polymerase delta or epsilon for the processing elongation of the leading (epsilon) lagging (delta) strands

Question 39

what is polymerase switching and when does it occur

Answer 39

the trade-off that occurs when polymerase alpha is done synthesizing the primer after the RNA-DNA primer hybrid is made, polymerase switching occurs and Pol alpha is replaced by Pol delta (lagging) and Pol epsilon (leading)