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

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

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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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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

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

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

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

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

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

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

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

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

DNA Replication Base Pairing DNA 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

DNA Replication Base Pairing DNA 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

DNA Replication Base Pairing DNA 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

DNA Replication Base Pairing DNA 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

DNA Replication Base Pairing DNA 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

DNA Replication Base Pairing DNA 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

3. DNA Zips Up 24

DNA Replication is complete Two 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

DNA Replication Review Step 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

DNA Replication: A Summary

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