1. DNA - Deoxyribose nucleic acid
Composed of nucleotides
store and transmit genetic information
replicate
undergo changes (mutate)

2. DNA (Deoxyribonucleic Acid)
Found in almost all living cells –in the nucleus of eukaryotes (3 Feet/Cell)
2 primary functions
Control protein (enzyme) production-These enzymes then control chemical reactions in cells.
Duplicate itself for new cells that are created

3. Nucleotide Deoxyribose sugar Phosphate group Nitrogenous base
A, T, C, G

4. Nitrogenous Bases 4 Bases Purine – Double ring
Adenine (A), Thymine (T), Cytosine (C), Guanine (G)
Purine – Double ring
A and G
Pyrimidine – single ring
T and C

5. Frederick Griffith: Transformation 1928
Discovered that bacteria could give other bacteria heritable traits, even after they were dead.

6. Avery, McCarty & MacLeod: Griffiths Refined (1944)
Refined Griffith's Experiment
Exposed R-strain Streptococcus to purified S-strain protein, and purified S-strain DNA
Only the bacteria exposed to the S-strain DNA were transformed

7. Hershey & Chase: The "Blender" Experiment (1952)
Worked with bacteriophages
Conclusively demonstrated that DNA was the molecule of heredity
Tagged phage DNA and protein with radioactive atoms and tracked the transmission of that radioactivity to infected bacteria
Nobel Prize: Hershey (1969)

9. Chargaff’s Rule Amount of guanine equals amount of cytosine
Amount of adenine equals thyamine
Chargaff’s rule: C=G A=T

10. Watson & Crick, Franklin & Wilkins (1953)

11. Two competing teams to determine the structure of DNA
Watson and Crick used X-ray diffraction data developed by Rosalind Franklin to develop their "double helix" model of DNA
Nobel Prize: Watson, Crick & Wilkins (1962)

12. James Watson and Francis Crick
DNA is a Double Helix
James Watson and Francis Crick
**Similar to ladder that is twisted**
Sugar and phosphate form the backbone
Bases lie between the backbone
Nucleotides
A, G, T, C
Held together by H-bonds between the bases
A-T – 2 H bonds
G-C – 3 H bonds

13. Orientation of DNA The nucleotides form a chain
Phosphate end is the 5' end
The opposite end (sugar) is the 3' end
Q: Since DNA is complementary, what end matches with the 5’ end?

14. Bases on one strand are covalently bonded to each other ("phosphodiester bonds")
Bases on opposite strands are hydrogen bonded to each other ("base pairs").
Adenine = Thymine (2 H bonds)
Cytosine = Guanine (3 H bonds)

15. Forms of DNA
Chromatin –Partially unwound (Normal Situations)
Chromosome – tightly wound DNA (Cell division)

16. Chromosome Structure DNA wraps around histones
Chromatin Fibers
DNA wraps around histones
histones form nucleosome
Histones
Nucleosomes

17. Plasmids small, circular, double-stranded DNA molecule
Different from chromosomal DNA
naturally exist in bacterial cells
Often provide bacteria with genetic advantages
antibiotic resistance
Hundreds to thousands of base pairs
each daughter cell receives a copy of plasmid
Bacteria can also transfer plasmids to one another through conjugation