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Discovering DNA structure

Discovering DNA structure. History activity. Erwin Chargaff. Worked with numbers of chemical molecules Look at the molecules in your bag These are VERY short DNA pieces Count up the number of Each molecule Do you see a trend? What is it?. Sugar – deoxyribose Phosphate – phosphate

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Discovering DNA structure

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  1. Discovering DNA structure History activity

  2. Erwin Chargaff • Worked with numbers of chemical molecules • Look at the molecules in your bag • These are VERY short DNA pieces • Count up the number of Each molecule • Do you see a trend? What is it?

  3. Sugar – deoxyribose • Phosphate – phosphate • A = adenine • T = thymine • G = guanine • C = cytosine

  4. Lord Alexander Todd Structure of nucleotide sugar (deoxyribose) phosphate a base: one of each of A, C, T or G Build as many nucleotides as you can = tape together - have to see letters/words

  5. James Watson and Francis Crick • Used others work to solve structure of DNA

  6. DNA is long and thin and has a repeating structure. • - Rosalind Franklin and Maurice Wilkins

  7. DNA has a backbone made of sugar and phosphate. • - Alexander Todd

  8. DNA is too wide to have just one backbone. • - Rosalind Franklin and Maurice Wilkins

  9. DNA is about [12 cm]* wide. • - Rosalind Franklin • (really, 20 Angstroms)

  10. The backbones of DNA are on the outside of the structure; bases are on the inside. • - Rosalind Franklin

  11. Bases can bond to each other within the same molecule using hydrogen bonds (weak bonds). • - J. M. Gullard and D. O. Jordan

  12. James Watson and Francis Crick • Solved true structure of DNA • Try to fit your nucleotides together – make DNA • So nucleotides match: • Guanine (G) bonds with Cytosine (C) • Thymine (T) bonds with Adenine (A)

  13. DNA structure • Describe it • Do you see how deoxyribose and phosphate chains on outside are opposite? • A-T • G - C

  14. DNA Structure • Shape is called double helix • You made a backbone – it is actually twisted around in a helix shape • Rosalind Franklin discovered “double helix” by doing X-ray diffraction • Can you gently twist your DNA model?

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