DNA replication

Question 1

When does DNA replication happen in the cell cycle

Answer 1

Interphase - s phase

Question 2

Semi conservative

Answer 2

DNA replication

Parent strand paired with daughter strand

Parent strand acts as template

Question 3

DNA replication

Answer 3

Strands separate , hydrogen bonds break due to DNA helicase

Both strands acts as a template

Free nucleotides attach

Complementary base pairing

DNA polymerase joins nucleotides

H bonds reform

Semi-conservative replication

Question 4

DNA helicase role

Answer 4

Breaking hydrogen bonds to separate strands

Strands then used as template

Question 5

DNA polymerase role

Answer 5

Joins nucleotides via a phosphodiester bond (+ condensation reaction) to form sugar-phosphate backbone in new strand

Question 6

Why is complementary base pairing important in DNA replication

Answer 6

Ensures new dna strand is exact copy of old DNA as it allows one strand to act as template to build new strand from

Question 7

Why arrows point in different directions

Answer 7

DNA strands run in anti parallel

Different ends of DNA have different molecular shapes

Only one end has complementary shape to active site of DNA polymerase

To from e-s complex so new nucleotides can be joined together at that point

Question 8

Explain why they used isotopes of nitrogen in their experiments

Answer 8

Labels nitrogenous bases in dna

By using heavy nitrogen first, labels parental dna so it can be traced through generations

By then moving to light nitrogen any new daughter strands will be traced and can be distinguished from parent strands