DNA Replication

Question 1

purpose of new dna/dna replication

Answer 1

• growth
• repair
• reproduction

Question 2

what replication method is used

Answer 2

semi-conservative

Question 3

what experiment determined the replication method dna uses?

Answer 3

meselon-stahl experiment

Question 4

triplet code

Answer 4

every 3 bases codes for one of the 20 a.a in dna
- determines how dna operates

Question 5

INITIATION PHASE

Answer 5

1. DNA GYRASE unwinds DNA
2. DNA HELICASE binds to origin and unzips DNA by breaking h bonds holding it together –> creates a BUBBLE or TWO FORKS
3. SSBPS attach to new exposed nucleotides to prevent them from reannealing/binding to each other again

Question 6

what occurs in the LEADING STRAND during ELONGATION

Answer 6

1. RNA PRIMASE attaches to parent chain and puts down RNA nucleotides (primers)
2. DNA POLY 3 binds to primer and adds complimentary nucleotides/bases TOWARDS the fork
3. once primase reaches end of fork, DNA POLY 1 attaches to end and dismantles it, replacing it with nucleotides

Question 7

what occurs in the LAGGING STRAND during ELONGATION

Answer 7

1. RNA PRIMASE attaches to parent chain and puts down RNA nucleotides (primers)
2. DNA POLY 3 binds to primer and adds complimentary nucleotides/bases AWAY from fork
3. another rna primase/dna poly 3 attaches upstream of OG primer (closer to fork) and repeats process
4. okazaki fragments created
5. DNA LIGASE binds okazaki fragments with phosphodiester bonds

Question 8

order of enzymes in leading strand replication

Answer 8

1. rna primase
2. dna poly 3
3. dna poly 1

Question 9

order of enzymes in lagging strand replication

Answer 9

1. rna primase
2. dna poly 3
3. dna poly 1
4. dna ligase

Question 10

dna poly 3 purpose

Answer 10

binds to rna nucleotides and creates complimentary nucleotides for parent strand

Question 11

dna poly 1 purpose

Answer 11

dismantles rna primase when it reaches end of parent strand and replaces it with complimentary nucleotides

Question 12

dna poly 2 purpose

Answer 12

• proof reads and fixe any mistakes by removing wrong nucleotides and replacing with the right ones
• makes sure h-bonds are present between bubble pairs

Question 13

dna ligase purpose

Answer 13

creates phosphodiester bonds to join okazaki fragments

Question 14

TERMINATION PHASE

Answer 14

• okazaki fragments dont properly match with parent strands bc rna primase is still in the way so theres no room for dna poly 1 to attach and dismantle it
• end of dna is snipped off
• dna naturally forms its double helix structure

Question 15

telomerase

Answer 15

replenishes telomeres, deactivated at a certain point