Biology 1201A Lecture Notes - Lecture 20: Synonymous Substitution, Molecular Clock, Molecular Evolution
14 Mar 2016
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Lecture 20 molecular convergence synonymous vs non synonymous mutations. Synonymous: if it doesn"t change the amino acid sequence. silent. Non synonymous: if it changes the aa sequence. ex: ser--> diff one if a mutation changes the phenotype, it has changed the aa sequence. Many random mutations don"t have a positive or negative effect, they just exist (neutral). Lots of changes to the nucleotide sequences which don"t affect the amino acid sequences, so there"s no selective advantage. *note: in the selection theory, all mutations would affect fitness. relationship between frequency of amino acid substitutions in given proteins vs. time since common ancestor. There are fewer amino acid differences in organisms that diverged more recently. The farther back in time you go, the bigger the differences are. This suggests something regular bc they are straight lines of change as a function of time (a rate).
