2. Erwin Chargaff Date of birth: August 11, 1905 in Ukraine He was a professor of biochemistry at Columbia University medical school He went to Yale and started investigating the chemical composition of lipids in Mycobacterium tuberculosis. He had one son, and a wife name Vera Broido.

3. Discoveries He used Rosalind Franklin’s X- ray diffraction studies of DNA. His findings strongly suggested that base-pairing existed within DNA between adenine and thymine, and between guanine and cytosine. Pairings like A-C, G-T, A-A, T-T, C- C, or G-G could not occur.

4. Discoveries Cont. Came up with the Chargaff rule. This first rule tells us that in natural DNA the number of guanine units is equal to cytosine and the number of adenine is equal to thymine. In humans- A=30.9% T=29.4% G=19.9% C=19.8%

5. Discoveries Cont. Cont. The second rule suggests the composition of DNA varies from one species to another.

6. Experiments Despite the fact that DNA samples from bacteria and humans are different they still observed the first rule using these two organisms. He was one of few to accept the unusual Avery report. Concluded that genetic differences among DNAs must be reflected in chemical differences among these substances.

7. Sources Used http://dna.microbiologyguide.com/516-components-of-dna-chemical-macromolecules- nucleotides/ http://dna.microbiologyguide.com/516-components-of-dna-chemical-macromolecules- nucleotides/ http://powerofthegene.com/joomla/index.php/jistory-of-genetics/erwin-chargaff http://en.wikipedia.org/wiki/Erwin_Chargaff Biology book http://library.thinkquest.org/20830/Textbook/HistoryofDNAResearch.htm# http://www.biologycorner.com/APbiology/DNA/13-2_DNA_structure.html http://post.queensu.ca/~forsdyke/bioinfo1.htm http://five30liveservice.wordpress.com/2012/10/02/does-our-dna-decide/ http://www.123rf.com/photo_12668156_bacteria-and-bacterium-cells-floating-in- microscopic-space.html http://www.123rf.com/photo_12668156_bacteria-and-bacterium-cells-floating-in- microscopic-space.html www.fanpop.com/clubs/puppies/images/9460947/title/friends-forever-wallpaper http://www.firstpeople.us/pictures/polar-bears/cute-polar-bear-cub-sitting-on-snow.html