lec 22 DNA replication

Question 1

what are the three hypothesized mechanisms of DNA replication?

Answer 1

conservative- one daughter DNA is all new and the other is old
dispersive- each daughter DNA molecule contains a mixture of new DNA
semiconservative- each daughter DNA contains one strand which is new and one which is old

Question 2

what is the Meselson-stahl experiment?

Answer 2

An experiment that shows evidence that DNA replication is semiconservative , separating DNA strands based on density using nitrogen isotopes (first N15 then N14)

Question 3

what are DNTPs?

Answer 3

They are the building blocks for DNA, composed of three phosphate groups attached to the 5’ carbon of deoxyribose

Question 4

what attacks the alpha phosphate on the incoming DNTP?

Answer 4

the 3’ OH at the primer end

Question 5

what are the two strands in DNA replication?

Answer 5

template strand- 3’-5’
coding strand- 5’-3’ needs a primer to encode

Question 6

what is the cofactor of DNA polymerase?

Answer 6

Mg2+

Question 7

what is DNA polymerase?

Answer 7

an enzyme that adds DNTPs on the 3’ end while Mg2+ stabilizes charges

Question 8

how does DNA polymerase know if base pairs are mismatched?

Answer 8

perfectly matched base pairs will fit nicely, while mismatched base pairs will not

Question 9

what is endonuclease and exonuclease?

Answer 9

an enzyme that cuts DNA strands internally and externally from the ends of the strand

Question 10

what are okazaki fragments?

Answer 10

short pieces of DNA synthesized on the lagging strand during DNA replication

Question 11

what is the oriC between?

Answer 11

a three 13bp sequence and a four 9bp sequence which is rich in A-T causing DNA unwinding

Question 12

what is bidirectional replication?

Answer 12

replication which occurs in two directions from the origin