1. DNA Replication

2. DNA Replication – What and Why Replication = DNA making copies of itself – DNA must be copied before a cell can divide – Each new cell will have a complete set of DNA

3. History of Replication Watson & Crick – realized that complementary base pairing provided a way for DNA to copy itself - base pairing could allow a new strand to be built on an old strand

4. DNA Replication In most prokaryotes, DNA replication begins at a single point and continues in two directions. In eukaryotic chromosomes, – DNA replication occurs at hundreds of places. – Replication proceeds in both directions until each chromosome is completely copied.

5. Critical Thinking Check How does the structure of a eukaryote and a prokaryote relate to the manner in which the DNA is replicated in each?

6. DNA Replication: Process Replication begins when the enzyme DNA helicase opens the DNA forming replication bubbles

7. DNA Replication: Process The nitrogen bases on the original DNA strands are exposed in the replication bubbles. They serve as a template to build new DNA strands

8. DNA Replication The ends of the replication bubbles known as the replication fork is where replication begins

9. DNA Replication – DNA Polymerase The enzyme DNA polymerase brings new nucleotides to the replication fork - it pairs them according to base pairing rules A pairs with T C pairs with G

10. DNA Replication The process continues until 2 complete copies of the DNA are produced Each copy of the DNA contains one strand of DNA from the original DNA molecule and one new strand that was produced by replication Known as semi-conservative replication

11. DNA Replication

12. Knowledge Check Summarize the major events that occur in DNA replication (you should come up with at least 3 unique steps).

13. Summary of DNA ReplicationDNA Replication 1.Hydrogen bonds between base pairs are broken 2.DNA unwinds – replication bubbles form 3.Free nucleotides pair up with their respective bases 4.DNA polymerase proofreads each new strand of DNA 5.Two double helices are now present