chapter sixteen part two

Question 1

basic process of DNA replication

Answer 1

DNA segment untwists, each parental strand serves was template for new strand

Question 2

how many nucleotides needed

Answer 2

4

Question 3

DNA polymerase III

Answer 3

adds DNA nucleotides to 3’ end of RNA primer
- most of DNA replication
- bacterial

Question 4

DNA polymerase I

Answer 4

removes and replaces RNA primer nucleotides with DNA
- bacterial

Question 5

primase

Answer 5

enzyme that synthesizes primer
- special RNA polymerase
- can start from scratch w/ just a template

Question 6

primer

Answer 6

RNA chain that is initial nucleotide chain
- 12 nuc. long

Question 7

helicase

Answer 7

enzymes that untwist the double helix at replication forks
- breaks hydrogen bonds
- requires ATP energy

Question 8

topoisomerase

Answer 8

enzyme that helps relieve superhelical tension ahead of replication fork
- breaks, swivels, and rejoins DNA strands
- breaks covalent bonds
- uses lots of ATP energy

Question 9

ligase

Answer 9

joins sugar-phosphate backbones of Okazaki fragments into continuous DNA strand

Question 10

ssDNA (single-strand)

Answer 10

binds to unpaired DNA strands to keep them from repairing

Question 11

replication origin

Answer 11

site where replication begins
- usually in spot with greater concentration of A/T

Question 12

replication bubble

Answer 12

2 strands of DNA separate to form bubble

Question 13

replication forks

Answer 13

where DNA splits into 2 strands (Y-shaped)

Question 14

which direction does the new DNA strand elongate?

Answer 14

5’ to 3’
- nucleotides added to 3’ end of primer/growing strand

Question 15

which direction is the original strand of DNA copied?

Answer 15

3’ to 5’

Question 16

leading strand

Answer 16

• only 1 primer required
• 1 per replication fork

Question 17

lagging strand

Answer 17

• elongated away from replication fork
• synthesized discontinuously into Okazaki fragments
• requires multiple primers

Question 18

Okazaki fragments

Answer 18

segments of lagging strands
- 100-200 nucleotides long in eukaryotes

Question 19

purpose of primer

Answer 19

to show DNA polymerase where to start synthesizing nucleotides

Question 20

steps of replication

Answer 20

1. helices unwinds parental strands
2. ssDNA binding proteins stabilize unwound strands
3. topoisomerase relieves strain ahead of replication fork
4. primase synthesizes RNA primer
5. DNA poly III synthesizes leading and lagging strand after primer/s made
6. DNA poly I replaces RNA w/ DNA by adding nucleotides to 3’ end of fragment
7. ligase forms bond between DNA of fragments

Question 21

proofreading

Answer 21

3’ to 5’ exonuclease activity, editing function

Question 22

nuclease

Answer 22

DNA cutting enzyme

Question 23

nucleotide excision repair

Answer 23

• removal of faulty nucleotides
• synthesis of new nucleotides
• ligase seals

Question 24

what enzyme proofreads during replication?

Answer 24

DNA polymerase III

Question 25

needed nucleotides for replication

Answer 25

dATP, dTTP, dGTP, dCTP
ATP, GTP, CTP, UTP

Question 26

what must an incoming nucleotide have?

Answer 26

3 phosphates
- polymerase rips off 2 P to make covalent (phosphodiester) bonds