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11.2 Structure of DNA

11.2 Structure of DNA. Actual structure of DNA was a complete mystery. Big question: How did DNA hold genetic information and what did it look like?. Inheritable genetic information is coded in the molecule called DNA ( Deoxyribonucleic Acid).

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11.2 Structure of DNA

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  1. 11.2 Structure of DNA

  2. Actual structure of DNA was a complete mystery Big question: How did DNA hold genetic information and what did it look like?

  3. Inheritable genetic information is coded in the molecule called DNA (Deoxyribonucleic Acid). DNA is a Polymer - built from monomers called Nucleotides 1. Deoxyribose Sugar - pentagonal ring 2. Phosphate Group - Phosphorus atom surrounded by four Oxygen atoms 3. Nitrogenous Base - a single or double ring of carbon and nitrogen atoms with functional groups

  4. Purines- double ring nitrogenous bases Adenine (A) & Guanine (G) Pyrimidines - single ring nitrogenous bases Thymine (T) & Cytosine (C)

  5. 1950 American Erwin Chargaff Analyzed different organism’s DNA: variation in number and amount of A, T, G, C Quantity of nucleotides in each organism he found A=T and G=C Chargaff’s Rule: Nucleotide number and concentration vary with each species. A=T and G=C within a specie’s DNA

  6. 1951 English Rosalind Franklin Studied molecules using X ray Diffraction Indicated a helix structure

  7. 1953 American James Watson and English Francis Crick Studying the structure of DNA Rosalind wrote to Watson and when he saw the X-Ray evidence he also believed DNA to be a Helix

  8. Complementary Base Pairing Each nitrogenous base must pair (bond) with its complementary base each fitting like a puzzle piece Adenine (A) pairs to Thymine (T) Guanine (G) pairs to Cytosine (C)

  9. Two long chains of nitrogenous bases bond with their base pair and form a ladder structure "Backbone" are the phosphate and deoxyribose "rung" of the ladder isthe Nitrogenous bases

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