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 Tetra nucleotide theory thought that DNA was uniform in all organisms and didn t have anything to do when genetic make up and isn t unique Replication occurs in the S phase of Interphase conservative or semi conservative or dispersive discovered to be semi conservative Parent molecules stay intact Nucleotides continue to be added to form the DNA polymer DNA polymerase stiches on nucleotides 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 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 Polymerase Chain Reaction cocktail contains extracted DNA 1 Heat DNA strand unwinds 2 cool down primer attaches to DNA 3 DNA polymerase attaches 4 End up with millions of copies of DNA Mutation Point mutation incorrect base pairing Point mutation inserted or deleted base DNA frame shift altered AA sequence In somatic cells mutations are passed along a line of cells i e within a single person are not heritable In germ line cells those that become egg and sperm
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