DNA replication

Question 1

semiconservative model:

Answer 1

parent DNA unwinds, and 2 new daughter strands have og one strand

Question 2

list 6 proteins involved in DNA replication

Answer 2

• helicase
• topoisomerase
• primase
• DNA polymerase
• single strand binding (SSB)
• DNA ligase

Question 3

topoisomerase:

Answer 3

breaks, rejoins and swivels DNA

Question 4

helicase:

Answer 4

untwist and separates DNA helix

Question 5

primase:

Answer 5

sythesises RNA primers

Question 6

DNA polymerase:

Answer 6

synthesises new DNA strand

Question 7

SSB:

Answer 7

single strand binding bind to single DNA strands and keep them from rejoining

Question 8

DNA ligase:

Answer 8

joins pieces of DNA together (forms phosphodiester bonds)

Question 9

how does replication begin:

Answer 9

at origins of replication, 2 DNA strands separated opening replication bubble

Question 10

which direction does the replication occur?

Answer 10

both directions of each origin

Question 11

list stages of DNA replication

Answer 11

initiation
elongation
termination

Question 12

initiation stage:

Answer 12

specific DNA sequence where helix is unwound/ open to enzymes
- helicase unwinds DNA strand

Question 13

elongation stage:

Answer 13

DNA polymerase add nucleotides to growing DNA strand

Question 14

termination stage:

Answer 14

end point of replication (where replication forks meet)

Question 15

replication fork is:

Answer 15

where the end of the bubble has the 2 new growing strands of DNA

Question 16

how does the leading strand replicate:

Answer 16

• DNA pol III starts synthesising
• continuous elongation from 5’ to 3’ direction
• ATTACHES to 3’ end of strand

Question 17

how does lagging strand replicate:

Answer 17

• primase makes RNA primer
• DNA pol III makes Okazaki fragment
• from 3’ to 5’ direction
• DNA pol detaches, next fragment primed and is replaces with DNA pol
• DNA ligase forms bonds btw fragments

Question 18

RNA primer:

Answer 18

short strand of RNA which enables binding of DNA pol, 5-10 nucleotides long

Question 19

leading strand:

Answer 19

synthesised in SAME direction of growing replication fork

Question 20

lagging strand:

Answer 20

synthesises AWAY from replication fork

Question 21

telomeres:

Answer 21

as linear DNA shortens after each replication, these are repeated sequences at end of chromosomes

TTAGGG repeated 100-1000 times in humans

Question 22

telomerase:

Answer 22

helps maintain length of telomeres

Question 23

define mutations:

Answer 23

changes in genetic material of cell

• source of new genes
• raw material of evolution/ natural selection
• could be positive, negative (deleterious) or neutral

Question 24

cause of mutations:

Answer 24

• errors in DNA replication

mutagens:

• from physical agents (xray, UV)
• chemical (tobacco, asbestos)

Question 25

protein helps cut out incorrect nucleotide: and mechanism

Answer 25

nuclease

nucleotide excision repair

Question 26

thymine dimers:

Answer 26

caused by UV light, extra bond inhibits normal DNA replication

nuclease - DNA pol - DNA ligase