1. DNA Replication

2. To make new cells through mitosis, DNA must be copiedTo make new cells through mitosis, DNA must be copied The DNA molecule produces two new complementary strands following the rules of base pairing: A-T, G-CThe DNA molecule produces two new complementary strands following the rules of base pairing: A-T, G-C Each strand of the original DNA serves as a template for the new strandEach strand of the original DNA serves as a template for the new strand

3. When and where does DNA Replication take place? S phaseinterphaseWhen - S phase in interphase of the cell cycle. Nucleus Where - Nucleus of eukaryotes Mitosis -prophase -metaphase -anaphase -telophase G1G1 G2G2 S phase interphase DNA replication takes place in the S phase.

4. DNA Replication DNA Replication Step 1 – Strand SeparationStep 1 – Strand Separation An enzyme separates or “unzips” the DNA strand at many points along the strand ReplicationFork Parental DNA Molecule 3’ 5’ 3’ 5’

5. DNA Replication Step 2 : - ReplicationStep 2 : - Replication 1. Each DNA strand serves as a template to form 2 new DNA molecules 2. Nucleotide bases are added to the strand according to the base-pairing rules. 2. Nucleotide bases are added to the strand according to the base-pairing rules. A-T, G-C A-T, G-C

6. DNA Replication Semiconservative Model:Semiconservative Model: Watson and Crick showed: 1.Watson and Crick showed: the two strands of the parental molecule separate, and each functions as a template for synthesis of a new complementary strand.. Parental DNA DNA Template New DNA

7. Question: What would be the complementary DNA strand for the following DNA sequence? DNA -GCGTATG-

8. Answer: DNA -CGCATAC-

9. DNA polymerases Special enzymes Move along new sections of copied DNA Checks for mistakes, removes and replaces mismatched nucleotides “Proofreading” reduces errors in DNA replication to about 1 error per 1 billion nucleotides!