E3 lecture1 - DNA structure and replication

E3 lecture1 - DNA structure and replication - 1 each DNA...

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DNA Structure and Replication Review: sequence of bases = sequence of amino acids Race to find structure of DNA - Watson and Crick (1953) - Linus Pauling - Rosalind Franklin/Maurice Wilkins X-ray diffraction was needed to elucidate structure (Crick) - showed that: DNA was a constant diameter (2 nm) Structure of DNA: - monomer unit is the nucleotide - base pairing: Adenine always pairs with Thymine Guanine always pairs with Cytosine Replication: - conservative or semi-conservative (or “dispersive”?) - discovered to be “semi-conservative.” Parent molecules stay intact. Steps: - occurs with help from an enzyme: DNA polymerase strings nucleotides together - polymerization of nucleotides is endergonic (i.e. a more complex molecule is formed)
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Unformatted text preview: 1) each DNA strand is a template 2) bases enter at attachment point as a triphosphate 3) two phosphates are cleaved – this provides the energy needed to attach the base 4) hydrogen bonds with template base More detail:- DNA unwinds (forms a “replication bubble”)- a “replication fork” forms- moves in opposite directions until synthesis complete Mutation- Point mutation: wrong base pairing- Point mutation: added (or deleted) base Editing out mistakes:- damage can occur from chemicals, UV light…- common mistakes:- depurination (loss of G or A) (can lose 10,000/day)- deamination- thymine dimers – from UV radiation … all errors result in the synthesis of a wrong protein...
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