2. HISTORY OF DNA A. Frederick Griffith – Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria. (1928) B.Rosalind Franklin - X-ray photo of DNA. (1952) C.Watson and Crick - described the DNA molecule from Franklin’s X-ray. (1953)

3. Watson & Crick proposed… DNA had specific pairing between the nitrogen bases: ADENINE – THYMINE ADENINE – THYMINE CYTOSINE - GUANINE CYTOSINE - GUANINE DNA is made of 2 long stands of nucleotides arranged in a specific way called the “Complementary Rule”

4. DNA Structure DNA consists of two molecules that are arranged into a ladder-like structure called a Double Helix. A molecule of DNA is made up of millions of tiny subunits called Nucleotides. Each nucleotide consists of: 1. Phosphate group 2. Pentose sugar 3. Nitrogenous base

5. Nucleotide Phosphate Pentose Sugar Nitrogenous Base

6. Nucleotides The phosphate and sugar form the backbone of the DNA molecule, whereas the bases form the “rungs”. There are four types of nitrogenous bases.

7. Nucleotides A Adenine T Thymine G Guanine C Cytosine

8. Nucleotides Each base will only bond with one other specific base. Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Form a base pair.

9. Nitrogenous Bases PURINES PURINES Adenine (A) 1.Adenine (A) Guanine (G) 2.Guanine (G) PYRIMIDINES PYRIMIDINES Thymine (T) 3.Thymine (T) Cytosine (C) 4.Cytosine (C) T or C A or G

10. BASE-PAIRING CG H-bonds T A Purine Purine Pyrimidine Pyrimidine

11. DNA Structure Because of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand.

12. G G A T T A A C T G C A T C

13. DNA Structure To crack the genetic code found in DNA we need to look at the sequence of bases. The bases are arranged in triplets called codons. A G G - C T C - A A G - T C C - T A G T C C - G A G - T T C - A G G - A T C

14. A gene is a section of DNA that codes for a protein. Each unique gene has a unique sequence of bases. This unique sequence of bases will code for the production of a unique protein. It is these proteins and combination of proteins that give us a unique phenotype.

15. Protein DNA Gene Trait

16. Your Task Draw a flow chart to show how to get from:

17. This powerpoint was kindly donated to www.worldofteaching.com www.worldofteaching.com http://www.worldofteaching.comhttp://www.worldofteaching.com is home to over a thousand powerpoints submitted by teachers. This is a completely free site and requires no registration. Please visit and I hope it will help in your teaching.