2.2 DNA replication

Question 1

in which phase of mitosis does DNA replication occur?

Answer 1

S phase

Question 2

describe the meaning of semi-conservative replication.

Answer 2

each DNA molecule has 1 old & 1 new strand

Question 3

describe the semi-conservative replication of DNA. (6)

Answer 3

1- DNA helicase unwinds & disrupts H-bonds linking base pairs
2- double helix separates
3- DNA polymerase adds free nucleotides by complementary base pairing
4- DNA polymerase rejoins nucleotides by a condensation reaction forming phosphodiester bonds
5- in the leading strand, replication is made continuously & in the lagging strand, replication is made in Okazaki fragments both from 5’ to 3’
6- 2 strands of identical DNA forms

Question 4

explain how the DNA strands are antiparallel.

Answer 4

5’ to 3’
3’ to 5’