Chapter 15 DNA Synthesis and Repair

Question 1

semiconservative replication

Answer 1

parental strand separate and each serves as a template for a new daughter strand

Question 2

conservative replication

Answer 2

the bases of both strands temporarily turned out from the nucleus, allowing for both strands to be copied, resulting in a completely identical double helix that is identical to the parent

Question 3

dispersive replicastion

Answer 3

parental double helix was cut at regular intervals and synthesize in short sections then the daughter strands would be a mix of old and new DNA segments.

Question 4

origin of replication

Answer 4

where the initial replication bubble forms

Question 5

replication fork

Answer 5

Y shaped region where the parental DNA is separated into single strands and copied

Question 6

DNA helicase

Answer 6

opens the double helix by breaking the hydrogen bonds between the base pairs

Question 7

DNA primase

Answer 7

synthesizes the RNA primer

Question 8

Single Strand DNA binding proteins

Answer 8

stabilize the single strand to prevents them from snapping back into a double helix

Question 9

topoisomerase

Answer 9

cuts and unwinds the double helix to relieve the twisting forces during replication

Question 10

DNA polymerase

Answer 10

synthesizes leading strand in the 5’ to 3’ direction

Question 11

sliding clamp

Answer 11

hold DNA polymerase in place during strand extension

Question 12

purpose of the RNA primer in DNA replication

Answer 12

DNA polymerase only works in the 5’ to 3’ direction but needs a 3’ end to extend from, RNA strand about 12 base pairs long will form to complement a strand with an OH at the end for the polymerase to bind to

Question 13

primase

Answer 13

a type of RNA polymerase that synthesizes the RNA primer

Question 14

discontinuous replication hypothesis

Answer 14

the DNA polyermase can only synthesize bases in the 5’ to 3’ direction, so primase synthesizes primers to which polymerase can connect too

Question 15

DNA ligase

Answer 15

catalyzes the formation of phosphodiester bonds between fragments, essentially forming the phosphate backbone and sealing up the double helices.

Question 16

replisome

Answer 16

a macromolecular machine made up of the proteins involved in replication

Question 17

telomere

Answer 17

the region at the end of the eukaryotic chromosome

Question 18

why is it difficult to replicate the end of a chromosome

Answer 18

somatic cells are unable to use the final RNA primer to replicate the end of the lagging strand

Question 19

telomersase

Answer 19

an enzyme that carries a sequence of the same repeating bases and attached to the overhanging section of unreplicated DNA. and allows polymerase to synthesize to the end of the DNA, keeping the telomeres from shortening.

Question 20

why do basticerial cells not need telomerase?

Answer 20

the chromosome in bacteria are a circle, there is to “end” that a primer falls short of and there is onely 1 replication point

Question 21

how does polymerase correct for mistakes

Answer 21

polymerase can proof read and remove mismatched pairs because they have a recodnizable shape

Question 22

nucleotide excision repair

Answer 22

used to remove damaged DNA, like the thymine dimers the result from UV light exposure