1. The Structure of DNA

2. Carries all the genes for your physical traits
Importance of DNA?
Carries all the genes for your physical traits
In the nucleus of ALL your cells
Codes for everything in your body

3. Watson and Crick
Discovered DNA structure 1953
Called DOUBLE HELIX –resembles spiral staircase.

4. DNA (deoxyribonucleic acid)
DNA nucleotides are made up of phosphate group, deoxyribose sugar, and a nitrogen base
1. Phosphate
Group 1 2
2. Deoxyribose Sugar 3
3. Nitrogenous Base

5. DNA (continued) Nitrogen Bases Purines=
Adenine and Guanine Pyrimidines=
Thymine and Cytosine
Base Pairing Rules
Adenine only bonds with Thymine
(A=T)
Guanine only bonds with Cytosine
(G=C)

6. Why does 1 purine HAVE TO bond with a pyrimidine?
#1. Look at the hydrogen bonds
Purine+purine= too wide
pyrimadine+pyramidine= too narrow
Purine+pyrimidine= width consictent with x-ray data found by Watson and clark
#2. Look at the width/size of the molecules

9. b A C D

10. Which is the ONLY correct base pair???G C A A A G A C T B G G C

11. A C B D
Which is the real Nucleotide???

12. Nucleic Acid Monomer (Label in your Notes)
Phosphate Group
5-carbon sugar
Nitrogen base

13. A=T
T=C
G=C
C=G
T=A A B C D

15. -Phosphates and sugars are connected by __covalent______bonds.
-Nitrogen bases are connected by a __hydrogen___ bond.
-Phosphates and sugars are connected by __covalent______bonds.
Covalent Bond

16. Explain to your shoulder partner the difference in bonding between A=T and C=G???

17. b A C D

18. A B C D Ionic Bonds Hydrogen Bonds Covalent Bonds Metallic bond
Which bonds connect nitrogen bases? Phosphates/sugars? A B C D

19. DNA (read only)
DNA is made of 2 long chains of nucleotides joined by hydrogen bonds
The end with the phosphate exposed is the 5’ end.
The other end with sugar exposed the 3’ end.
DNA Structure

21. The Double Helix

22. DNA DNA is almost always wrapped around proteins called histones.
…. not this is what’s found in the cell.
DNA
DNA is almost always wrapped around proteins called histones.
The histones are the proteins that we cut with the enzyme in our DNA extraction lab.
chromatin
This ….