DNA - replicas to be made Strands separate; new nucleotides...

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1/8/11 1 DNA Macromolecules Very large molecules Many are polymers = long chains of monomer subunits Nucleic acids, proteins, carbohydrates Nucleic acids: RNA, DNA Monomer unit is nucleotide = phosphate, sugar, nitrogenous base The sugar is either ribose (RNA) or deoxyribose (DNA) Structure of DNA Watson and Crick, 1953 Model based on X-ray crystallography by Franklin and Wilkins Four DNA bases Adenine (A) Thymine (T) Guanine (G) Cytosine (C)
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1/8/11 2 The DNA helix Built like a spiral staircase “Handrails” are made by linking sugars and phosphates “Steps” are made of pairs of bases Base pairing A always pairs with T C always pairs with G Hydrogen bonds hold them together across the double helix Replication Base pairing rules allow exact
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Unformatted text preview: replicas to be made Strands separate; new nucleotides added Result: two identical double helices DNA Polymerase Enzyme that replicates DNA Matches complementary nucleotides, connects sugar & phosphate Mistakes in base pairing About 1 in 100,000 DNA polymerase repairs almost all mistakes (proofreading) Remaining mistakes are mutations Mutation = any change in sequence of DNA bases 1/8/11 3 Results of Mutation Usual result: No effect Sometimes: Harmful (defective protein) Rarely: Evolutionary advantage Cancer Mutations accumulate over years of exposure to mutagens (chemicals, radiation, etc.) Finally, one cell multiplies out of control...
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This note was uploaded on 04/15/2011 for the course BIOL 101l taught by Professor Huddleston,m during the Fall '08 term at University of Hawaii, Manoa.

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DNA - replicas to be made Strands separate; new nucleotides...

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