Schwabe 5 DNA replication & repair

Question 1

POLARITY all 3 DNA polymerases work exclusively

Answer 1

5’->3’

Question 2

OKAZAKI strands

Answer 2

leading strand synthesized continuously, lagging strand discontinuously

Question 3

PRIMERS:

Answer 3

chunks of DNA s fragments

Question 4

DNA LIGASE

Answer 4

• SEALING NICKS of DNA polymers ease phosphodiester backbone

Question 5

DNA TOPOISOMERASES

Answer 5

control superhelical density

-in bacteria differs significantly to mammablian enzyme

Question 6

DNA GYRASE:

Answer 6

enzyme essential for bacterial growth, catalyses ATP dependent negative supercoiling of DNA circles. => antibiotics inhibit DNA gyrase

Question 7

HELICASE:

Answer 7

ATP – dependent DNA unwinding => hydrolysis,

Question 8

SSB PROTEIN:

Answer 8

binds to ssDNA, stablises helicase

=> Move away from fork down DNA

Question 9

PRIMASE:

Answer 9

puts RNA primers (5-10 nucleotides long extended by DNA Pol III ( 2 per fork)) on both DNA template strands

Question 10

PRIMOSOME

Answer 10

multi-protein complex, recognises origin & sites primase should put primers on

Question 11

Okazaki fragments =

Answer 11

1-2000 nucleotides long.

Question 12

RNA primers:

Answer 12

removed by DNA Pol I 5’->3’ nuclease, uses DNA Pol I 5’->3’ polymerase to fill gaps

Question 13

DNA REPLICATION IN EUKARYOTES

DIFFERENCES:

Answer 13

multiple linear chormosomes, not circular.
Multiple forms of DNA polymerase, multiple origins of replication & many more replication forks.
“extra” step => DNA histone re/dissociation

Question 14

E.coli: use Pol 1 & Pol III for

Answer 14

3’->5’ exonuclease to proof read

Question 15

UV radiation

Answer 15

=> covalent linking in adjacent pyrimidines within same strand of DNA => Thymine dimers commonly formed.

Question 16

LESIONS

Answer 16

leathal in strains (e.g. polA1) cannot correct themselves, block DNA replication

Question 17

EXCINUCLEASE

Answer 17

), DNA pol I, DNA ligase: removal of T-T dimers

Question 18

DNA Polymerase I

Answer 18

5'->3' nuclease
primer removal & repair of lesions
5'->3' polymerase
gap filling
3'->5' exonuclease
error correction