1. 1 DNA Replication Preparing for mitosis or meiosis copyright cmassengale

2. 2 Replication Facts DNA has to be copied before a cell dividesDNA has to be copied before a cell divides DNA is copied during the S or synthesis phase of interphaseDNA is copied during the S or synthesis phase of interphase New cells will need identical DNA strandsNew cells will need identical DNA strands copyright cmassengale

3. 3 DNA Replication Enzyme Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds.Enzyme Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds. Two strands open forming Replication Forks (Y- shaped region)Two strands open forming Replication Forks (Y- shaped region) copyright cmassengale ReplicationFork Parental DNA Molecule 3’ 5’ 3’ 5’

4. 4 DNA Replication An enzyme called DNA polymerase grabs new nucleotides found floating in the cell and adds the new complimentary nucleotides to the single DNA Strand.

5. DNA Replication As the new nucleotides are attached Covalent bonds form between the sugar of one nucleotide and the phosphate of the other nucleotide. copyright cmassengale5

6. DNA Replication Because each DNA strand is so long replication does not happen in just one location of he Chromosome. Multiple bubble of polymerase will be adding new bases at the same time. Once done the polymerase falls off. 6

7. DNA Replication In each new DNA strand one side of the double helix is the original molecule and the other side is the new strand. This is called Semi-Conservative replication. 7

8. 8 Replication of Strands copyright cmassengale

9. 9 Proofreading New DNA DNA polymerase initially makes about 1 in 10,000 base pairing errorsDNA polymerase initially makes about 1 in 10,000 base pairing errors Enzymes proofread and correct these mistakesEnzymes proofread and correct these mistakes The new error rate for DNA that has been proofread is 1 in 1 billion base pairing errorsThe new error rate for DNA that has been proofread is 1 in 1 billion base pairing errors copyright cmassengale

10. 10 Question: What would be the complementary DNA strand for the following DNA sequence?CGTATG copyright cmassengale