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
* \
1. Double helix is opened by the enzyme helicase at the origins of replication
* helicase breaks open the hydrogen bonds between bases
* \
2. 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