Unit 3 - Replication and repair

Question 1

Conservation Model

Answer 1

• parental DNA would make TWO NEW DNA strands
  -the new daughter strand would joing to from one double helix and the original parent DNA remain as its start DH

Question 2

Semi - Conservative model

Answer 2

• TWO NEW DAUGHTER strand were replicated would bind to a parent strand to form a double helix
• this each DNA mol of first replication would contain a parental strand

Question 3

Dispersive Model

Answer 3

-Parental strand broke into SMALL FRAGMENTS
-at end each small fragment bind to pieces of newly copied DNA completing DH
-each one contains PARENTAL FRGAMENTS and newly synthesized fragments

Question 4

DNA replication process (3)

Answer 4

1) produces two identical copies of the chromosome during S phase
2) catalyzed by my enzymes including: DNA, polymers, helicase, ligase, and primase
3) replication takes place at point where the DNA DH sperates called the replication fork

Question 5

Initiation of DNA Replication

Answer 5

a portion of the DNA double helix unwinds to expose the bases for new pairing

Question 6

Elongation of DNA Replication

Answer 6

2 new strands of DNA r assembles using parental DNA as a template

Question 7

Termination Phase of DNA Replication

Answer 7

the DNA replication process is completed and the 2 new DNA mols sperate

Question 8

Organization of DNA

Answer 8

in order to fit within a cells nucleus DNA is packed tightly coiled structures called chromatin which unravel prior to replication

Question 9

Initiation Phase in-depth

Answer 9

• before DNA replication can begin the double helix structure of DNA mol must be unwound from each other

Question 10

Helicase (initiation phase)

Answer 10

breaks the hydrogen bonds that holds complete nitrogenous bases of DNA together.

Question 11

Point of separation (initiation phase)

Answer 11

creates a ‘y’ shape called a replication fork and the 2 parent DNA strands now act as templates for making new strands of DNA

Question 12

Replication origin

Answer 12

the starting point for replication

Question 13

separating the DNA has challenges

Answer 13

1) tension from unravelling DH can lead to twist and tangle
solution ; topoisomerase
2) annealing strands have a tendency to rejoin or anneal
solution ; ssbs

Question 14

Topoisomerase

Answer 14

the enzyme that relieves tension caused by the unwinding of parent DNA; they cleave DNA strands, allows the strand(s) to untwist

Question 15

Single Strand binding proteins

Answer 15

(SSBs) r enzymes that bind to the separated strands to prevent rents DNA strands from them coming back together

Question 16

Direction to DNA replication

Answer 16

towards direction or replication for on one strand and away on the other ( 5’ to 3’)

Question 17

in eukaryotes more then one replication fork

Answer 17

this may exist on a DNA mol as a reuslt when two replications fork r near a replication bubble is made

Question 18

replication bubbles

Answer 18

a the separation of DNA in both directions during replication

Question 19

Elongation Phase

Answer 19

• DNA polymerase 3 builds a new complementary DNA strand by + new nucleotides
• use nucleoside triphosphate as building blocks

Question 20

RNA Primase

Answer 20

lays down RNA primers (10-60 RNA bases) to be used by DNA polymerase as a taring point for the new strands

Question 21

DNA Polymerase 3

Answer 21

• adds complementary bases (a-t and c-g)
• always needs a template strand
• uses RNA primers as a starting point

Question 22

Job of DNA polymerase 3

Answer 22

they proofread or check their work removing the vast majority of wrong nucleotides that r accidentally added to the chain

Question 23

Nucleoside Triphosphate

Answer 23

is a ml containing a nitrogenous base bound to a 5c sugar w 2 phosphate groups bound to the sugar

Question 24

Leading strand

Answer 24

is the DNA strand that is copied continuously in the direction towards the replication fork
- quickly
- 5’ to 3’

Question 25

Lagging strand

Answer 25

is the DNA strand that is copied away from the replication for
- 5’ to 3’
- much slower process

Question 26

DNA polymerase 3 (lagging strand)

Answer 26

adds nucleotides from primers to primer making Okazaki fragments

Question 27

Okazaki fragments

Answer 27

is a series of RNA primers and short DNA fragments on lagging stand

Question 28

DNA polymerase 1

Answer 28

replaces RNA primers w appropriate Deoxyribonucleotides. but a gap if left between fragments

Question 29

DNA Ligase

Answer 29

joins fragments by creating phosphodiester bonds

Question 30

Termination Phase

Answer 30

eventually two replication forks will fuse together and make a continuous strand of newly synthesized DNA

Question 31

Termination Phase: DNA polymerase enzymes carry out replication proofreading correcting errors

Answer 31

-most often base pairs mismatches; DNA polymerase 3 cannot go forward if base pair r mismatched. usually back up replaces the incorrect base pair w the correct one

Question 32

Termination Phase: rare occasions

Answer 32

(1 error for every 1 million base pairs) a mismatched base pair error is present after replication is complete

Question 33

Termination Phase: special DNA repair…

Answer 33

they repair mechanisms which include DNA polymerase 1 and DNA polymerase 2 read the strand for errors.

Question 34

Termination Phase: DNA polymerase 2

Answer 34

is a slow enzyme and often works to repair damage to DNA that occurs between replication events

Question 35

during lagging synthesis, ligase joins together multiple Okazaki fragments (t or f)

Answer 35

T

Question 36

in DNA replication which of the following events happens during both leading and lagging strand synthesis

Answer 36

RAN primers helps initiate DNA synthesis