1. DeoxyriboNucleic Acid
DNA
DeoxyriboNucleic Acid

2. DeoxyriboNucleic Acid
DNA
DeoxyriboNucleic Acid

3. DNA is made of units called nucleotides
The DNA Code is formed by Nitrogen bases

4. Nucleotides are in 3 parts
Nitrogen Base
Phosphate
Sugar (deoxyribose)

5. There are 4 Nitrogen Bases in DNA that make up the code
A – Adenine
T – Thymine
G – Guanine
C – Cytosine

6. There are 2 types of Nitrogen Bases
A) Purines – Adenine and Guanine
double ring
B) Pyrimidines – Thymine and Cytosine single ring

7. The nitrogen bases bond together with weak hydrogen bonds
A only bonds to T
C only bonds to G
A - T and C - G are base pairs

8. Example sequence
A -
T -
C -
G -

9. Example sequence
A - T
T -
C -
G -

10. Example sequence
A - T
T - A
C -
G -

11. Example sequence
A - T
T - A
C - G
G -

12. Example sequence
A - T
T - A
C - G
G - C

13. The chains of nucleotides form a sequence which is the genetic code

14. DNA Structure
DNA forms a twisted ladder structure called a double helix

15. Watson and Crick
Discovered the Double Helix
DNA structure

16. DNA “Ladder”
Rungs (steps) of the ladder are the Nitrogen base pairs connected with weak hydrogen bonds
Sides of the ladder are the phosphates and the sugars (deoxyribose) connected with strong covalent bonds like a backbone

17. DNA Replication DNA duplicates itself before mitosis
This occurs in the S phase of cell cycle

18. Semi conservative model
The two DNA strands split before replication

19. A-T has 2 hydrogen bonds C-G has 3 hydrogen bonds

20. Replication
The weak hydrogen bonds “unzip” and new nucleotides are attached on each side according to base pair rules. A-T C-G

21. DNA Replication Video
Show beginning

22. Each nucleotide has 2 ends named for the carbon on the sugar it attaches to, Either 3’ or 5’.
The 3’ end always attaches to the 5’ end with a phosphate in between

23. The sides of the DNA molecule are STRONG
So the DNA Code will stay intact

24. PERFECT COPIES?
DNA must be replicated perfectly so the new cells that form are identical
There are proofreader enzymes to ensure copies are made correctly

25. ENZYMES Helicase – Breaks apart the DNA strands
Primase – Builds a short RNA primer to start the chain
Polymerase – Elongates DNA strand by Attaching new nucleotides
can only read in 3’ to 5’ direction
Elongates in the 5’ to 3’ direction

26. Direction of DNA
Leading strand - Side made continuously in one direction
Lagging strand – Side made away from replication fork

27. Okazaki Fragments
Short segments of DNA that make lagging strand

28. Ligase
Enzyme that connects Okazaki fragments

29. End of replication problem
Removal of RNA primer leaves gap
Telomeres – non coding repetitions at end
Telomerase enzymes that lengthen telomeres

30. Telomeres PROTECT ends of Chromosome
If telomeres did not wear away, some scientists think it would prolong life

31. DNA Replication Video
DNA rap – Blame it on the DNA