DNA replication 1

Question 1

how many hydrogen bonds are in A:T and G:C respectively

Answer 1

A:T - 2 Hydrogen bonds. G:C - 3 hydrogen bonds

Question 2

what is the equation for the linking number

Answer 2

linking number = twist + writhe

Question 3

how do you calculate twist and writhe

Answer 3

twist = DNA size divided by 10, writhe = number of times double helix passses over itself

Question 4

what is the two states of circular DNA

Answer 4

Relaxed and supercoiled

Question 5

what is the two states of supercoiled DNA

Answer 5

Positive and Negative

Question 6

what does negative supercoiling do

Answer 6

facilitates DNA strand separation

Question 7

what does positive supercoiling do

Answer 7

inhibits DNA strand separation

Question 8

when are DNA strands separated

Answer 8

during replication and transcription

Question 9

what alters the tension of supercoiling?

Answer 9

topoisomerase 1/2 and DNA gyrase with ATP.

Question 10

what is the main difference between topoisomerase 1 and 2?

Answer 10

topoisomerase 1 nicks a single strand to pass the other strand through gap before resealing it. topoisomerase 2 nicks the two strands and pass through the duplex gap before resealing nick

Question 11

is DNA gyrase energy dependent ?

Answer 11

yes

Question 12

does positive supercoiling require energy

Answer 12

yes

Question 13

does negative supercoiling require energy

Answer 13

yes

Question 14

what are the two steps of replication strategy

Answer 14

1 converts ssDNA circle to dsDNA circle 2 initiate rolling circle replication

Question 15

what is the oriC ?

Answer 15

where DNA replication is recognised and bound by initiator proteins

Question 16

what is an initiator protein ?

Answer 16

a protein which is responsible for recruiting more proteins to begin replication

Question 17

what direction does the OriC go in?

Answer 17

bidirectionally with two forks

Question 18

what do you call the end point of the oriC

Answer 18

the terminus

Question 19

what are the 3 steps of the polymerase mechanism?

Answer 19

1. substrate binding. 2.nucleotide incorporation 3. translocation

Question 20

what are the 3 core complexes of subunits

Answer 20

alpha, beta and omega

Question 21

what does the alpha subunit do

Answer 21

DNA polymerizing activity

Question 22

what does the beta subunit do

Answer 22

3’-5’ exonuclease

Question 23

what does the omega subunit do

Answer 23

stimulates beta

Question 24

what is the sliding clamp loader complex?

Answer 24

a protein complex that prevents DNA polymerase falling off during replication and loads itself onto DNA during replication

Question 25

give the 5 steps of the sliding clamp loader complex

Answer 25

1 clamp binds to DNA polymerase and ATP 2 complex opens clamp, places on DNA. 3 hydrolyses ATP releases energy closes clamp around DNA 4 DNA polymerase binds to clamp 5 DNA synthesis begins

Question 26

is the sliding clamp loader complex semi conservative?

Answer 26

yes

Question 27

can the sliding clamp loader complex synthesize DNA de novo?

Answer 27

no

Question 28

what is each strand used as a template for in sliding clamp loader complex

Answer 28

synthesis of a new strand

Question 29

are the two strands parallel or anti parallel?

Answer 29

anti parallel

Question 30

what is an okazaki fragment

Answer 30

short, newly synthesized DNA fragments strand that is synthesized on the lagging strand during DNA replication

Question 31

what is the lagging strand

Answer 31

the strand of DNA synthesized in the opposite direction of the replication fork movement

Question 32

what is DNA A

Answer 32

an initiator protein

Question 33

what is DNA B

Answer 33

replicative helicase- separates the two DNA strands. Located on the lagging strand

Question 34

what is DNA G

Answer 34

DNA primase - synthesizes new okazaki fragments

Question 35

what is SSB

Answer 35

single stranded DNA binding protein that always coats ssDNA, confers rigidity

Question 36

what is the ORC

Answer 36

The origin recognition complex (ORC) is a multi-subunit protein complex that recognizes and binds to the origin of replication on DNA to initiate DNA replication.