DNA Replication

When does it take place?

S phase of cell cycle

Purines

Adenine & Guanine

Pyrimidines

C, U, T

5’ end has a….group

phosphate

3’ end has…group

hydroxyl

What are the 3 models of DNA Replication?

1. Conservative - both strands either new or old

2. Semiconservative

3. Dispersive - more broken up

What is the correct model for DNA replication? What confims this?

1. Semiconservative - 1 old stand, 1 new strand

2. 2 areas of density confirm it

Which direction is DNA synthesized?

5’ → 3’ direction

Mismatch Repair

repair enzymes correct base pair errors

Nucleotide Excision Repair

nuclease cuts out & replaces damaged stretches of DNA

Telomeres

special nucleotide sequence @ end of chromosomes

TTAGGG repeats 2,500x

slows erosion of genes near end of DNA but DOESN’T prevent shortening of DNA