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

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

3. 3

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

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 18

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 19

20. 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

21. 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

22. 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

23. 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

24. 3. DNA Zips Up 24

25. 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

26. 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

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