1 DNA Replication EQ: How does the cell replicate the DNA in preparation for nuclear division. 1

2 Occurs in the nucleus during theDNA Replication Occurs in the nucleus during the S Phase Of Interphase 2

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4 DNA Replication Big Picture: A new and identical molecule of DNA is made, using the old one as a template The # of chromosomes doubles. Humans: Instead of 46 individual chromosomes, we now have 46 sets of chromosomes. 4

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9 DNA Replication Making an exact copy of each strand of the DNA molecule before Mitosis Involves 3 easy steps… 1) Helicase unzips DNA 2) DNA polymerase creates a complementary strand for each side of the molecule 3) Two DNA molecules result, neither one is completely new Before DNA Replication After DNA Replication 9

10 DNA Replication: 1) DNA UnzipsHELICASE A G T C This animation of DNA unzipping will proceed on it’s own 10

11 DNA Replication DNA UnzipsG HELICASE This animation of DNA unzipping will proceed on it’s own 11

12 DNA Replication DNA UnzipsG HELICASE This animation of DNA unzipping will proceed on it’s own 12

13 DNA Replication DNA UnzipsG HELICASE This animation of DNA unzipping will proceed on it’s own 13

14 DNA Replication DNA UnzipsG This animation of DNA unzipping will proceed on it’s own HELICASE 14

15 DNA Replication DNA UnzipsG This animation of DNA unzipping will proceed on it’s own Left Strand of Original DNA Right Strand of Original DNA 15

16 2. Base Pairing DNA polymerase brings in complementary bases for both sides of the DNA strand in the open helix. 16

17 DNA Replication Base PairingLeft Strand Original DNA This animation of DNA pairing up will proceed on it’s own Right Strand Original DNA 17

18 DNA Replication Base PairingDNA Polymerase Left Strand Original DNA This animation of DNA pairing up will proceed on it’s own Right Strand Original DNA New Right DNA Strand 18

19 DNA Replication Base PairingDNA Polymerase Left Strand Original DNA This animation of DNA pairing up will proceed on it’s own Right Strand Original DNA New Right DNA Strand 19

20 DNA Replication Base PairingDNA Polymerase Left Strand Original DNA This animation of DNA pairing up will proceed on it’s own Right Strand Original DNA New Right DNA Strand 20

21 DNA Replication Base PairingDNA Polymerase C G G Left Strand Original DNA Have students notice that there are two strands of DNA that are exactly alike Right Strand Original DNA New Right DNA Strand New Left DNA Strand 21

22 DNA Replication Base PairingDNA Polymerase G C G C G G Left Strand Original DNA This animation of DNA pairing up will proceed on it’s own Right Strand Original DNA New Right DNA Strand New Left DNA Strand 22

23 DNA Replication Base PairingDNA Polymerase DNA Replication Base Pairing A A T T C C G G C G G Left Strand Original DNA This animation of DNA pairing up will proceed on it’s own Right Strand Original DNA New Right DNA Strand New Left DNA Strand 23

24 3. DNA Zips Up 24

25 DNA Replication is completeTwo identical strands of DNA! “Semi-conservative” –neither of them is 100% totally new. Each is 50% old and 50% new. T C A G 25

26 DNA Replication ReviewStep 1 Step 2 Step 3 Step 1 – DNA unzips Step 2 – Complementary bases match with each DNA strand in the open helix Step 3 – DNA zips up 26

27 DNA Replication: A Summary

28 DNA Proofreading DNA polymerase proofreads each nucleotide as it is added to the DNA strand If there’s a mistake… it backs up removes the wrong nucleotide adds the right nucleotide