DNA Replication
Replication copies the genetic information
What is replication?
- Making another copy of DNA
When does replication take place?
- During synthesis of interphase
- Makes a copy of itself during mitosis and meiosis
Why does replication happen?
- Done in order to ensure all cells in body have same information
Watson/Crick model gave clues to how DNA replicates
- Base pairing rule
- If one strand is known, the sequence of the other strand is also known
- Therefore, a single strand of DNA can serve as a template for a new strand
Proteins carry out the process of replication
- Helicase (enzymes)
- unzip double helix by breaking hydrogen bonds
- Hold strands apart
- DNA polymerases (enzymes)
- Enzymes that bond free nucleotides to each template strand of DNA
Steps in DNA replication
- \
- Double helix is opened by the enzyme helicase at the origins of replication
- helicase breaks open the hydrogen bonds between bases
- \
- Free nucleotides are added to form base pairs according to Chargaff’s rules by an enzyme called DNA polymerase
- 3.DNA polymerase causes the hydrogen bonds to form new rungs again and sugar phosphate bonds form to create new side
- resulting in two new identical DNA molecules
- Each have one original side and one new side
- Semi-conservative replication
Replication is fast and accurate
- Fast:
- 50 nucleotides added per second
- starts at many origins of replication
- Accurate:
- DNA polymerase -- spell check
- Detects and removes incorrect nucleotide
- replaces with correct nucleotide
- So that only 1 in every 1,000,000,000 nucleotides is wrong