DNA

1928 studying disease (pneumonia) Griffith 1928 studying disease (pneumonia) Experiments showed that there is a substance within bacteria that causes disease.

Wanted to know if DNA or protein carried genetic material Experiment 1: He injected protein destroyers Experiment 2: He injected DNA destroyers Results: DNA is genetic material AVERY

DNA stands for deoxyribose nucleic acid 2 DNA stands for deoxyribose nucleic acid This chemical substance is present in the nucleus of all cells in all living organisms DNA controls all the chemical changes which take place in cells The kind of cell which is formed, (muscle, blood, nerve etc) is controlled by DNA The kind of organism which is produced (buttercup, giraffe, herring, human etc) is controlled by DNA

DNA’s Appearance DNA is composed of many smaller units that we call nucleotides. This is similar to the many small beads that make up a necklace.

Nucleotide Consists of 3 parts: 1) Deoxyribose Sugar 2) Phosphate 3) Nitrogen Base

Nitrogen Bases Can vary between four: 1) Adenine (A) 2) Guanine (G) 3) Cytosine (C) 4) Thymine (T)

Nitrogen Base Groups Adenine and Guanine consist of the Purines. Cytosine and Thymine consist of Pyrimidines.

Structure of DNA

D) Erwin Chargaff In 1949, Chargaff discovered that the amount of A always equaled T, and G always equaled C. Chargaff’s Rules: A pairs with T G pairs with C

Complimentary Base Pairing

E) Rosalind Franklin In 1952, Franklin used x-rays to find that a DNA molecule resembled a tightly coiled spring (helix). * Franklin died at age 37 of cancer due to x-rays.

Franklin’s Experiment

F) Watson and Crick In 1953, using the discoveries of the other scientists, Watson and Crick, completed the first model of DNA. They also found that the bases were joined by hydrogen bonds.

Any Questions? “Life is not easy for any of us. But what of that? We must have perseverance and above all confidence in ourselves. We must believe that we are gifted for something and that this thing must be attained.” --Marie Curie