1. DNA Replication

2. DNA Replication
DNA is replicated during the “S” stage of the cell cycle. DNA replication is necessary for both Mitosis and Meiosis. Mitosis- growth, repair, and to maintain surface to volume ratio. Meiosis- produce gametes

3. DNA Synthesis
Occurs in both Prokaryotes and eukaryotes. It take place in the nucleus of eukaryotes. It produces two identical copies of DNA. It is controlled by several different enzymes; helicase and DNA polymerase A G C T A G C T

4. Replication controlled by Enzymes
Helicase- unzips the hydrogen bonds exposing the nitrogen bases. A replication fork is created (Y shaped region). New strands are produced at the forks. Replication – base pair rules A - T G - C

5. Synthesis
DNA polymerase adds new nucleotides at the replication fork. New nucleotides can only be added at the 3’ end of the DNA.
RNA
Primer
DNA Polymerase
Nucleotide 5’ 3’

6. DNA Replication Replication Fork Point of Origin
DNA replication 1.42

7. DNA Replication and Mutations
In humans, DNA replicates approximately 50 nucleotides per second. or 3,000 nucleotides per minute Base pair errors are made during replication. Mutation is a change in the genetic code.

8. Preventing Mutations during Replication
DNA polymerase makes about 1 in 10,000 errors. Enzymes (DNA polymerase) act as “Spell Checkers” correcting the errors. Proof reading results in only 1 error in 1 billion base pairs.

9. Semi- Conservative Model
Watson and Crick recognized from their model, that the DNA could be easily copied. The original strand is opened and copied, following base pair rules. The resulting 2 identical strands of DNA are composed of both an original (parental) and a new copy.
1958- Meselson and Stahl confirm the semi-conservative model with an experiment

10. Semi- Conservative Model
Each of the two new strands of DNA are composed of: One original (parent) strand One new strand Both are identical in every way

11. DNA and Replication (13 min).