Unit # 2: Molecular Genetics - PowerPoint PPT Presentation

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Unit # 2: Molecular Genetics

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  1. Unit # 2:Molecular Genetics

  2. DNA • Long form: • Function: • Location: • Structure: Deoxyribonucleic acid Store hereditary material Nucleus Double helix

  3. 1944 History of DNA 1920 1949 • Timeline Time! Using the year you’ve been given and the information on pages 206 -209 in your textbook write out what you know: • Scientists involved • Experiment performed • Discovery Share your information with the class. 1953 1869 1952 1930

  4. Chemical Composition of DNA Nucleotides: • Deoxyribose sugar • Phosphate group • Nitrogenous base or

  5. Variations in DNA • Nitrogenous Bases Four different bases:

  6. Complementary Pairing One purine + one pyrimidine A-T pairing G-C pairing A= T G=C purines=pyrimidines

  7. Nucleotide Ester bond Glycosyl bond Glycosyl bond: between a sugar and organic molecule by way of an intervening nitrogen or oxygen atom Ester bond: formed by the condensation of a carboxyl group ( C=O) with a hydroxyl group (-OH)

  8. ssDNA Polymer • DNA is composed of many nucleotides held together by phosophodiester bonds 1 2 3 4

  9. Phosphodiester bonds • Covalent bond between a phosphate group and 3’ carbon of one sugar and the 5’ carbon of another. • Makes up the sugar-phosphate backbone of DNA. 5’ 3’ 5’ 3’ 5’ 3’

  10. DNA Structure: Double Helix • DNA consists of anti-parallel strands of nucleotides • Bases of one strand are paired with bases in the other strand facing inward toward each other: complementary base pairing

  11. Anti-parallel DNA • One strand runs 5’-3’ and the other runs 3’-5’ • Intrinsic directionality • If you know the sequence on one strand, you know the sequence on the complimentary strand • 5’ end- phosphate group • 3’ end- hydroxyl group

  12. DNA Continued.... • Clock-wise (right-handed) helix • Diameter of DNA: 2nm -if T+C (pyramidines) = < 2nm at some points -if A+G (purines) = > 2nm at some points • Complete turn every 10 nucleotides (3.4 nm) • Distance between adjacent base pairs (0.34 nm)