BIO120H1 Chapter 5: Chapter 5.docx
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BIO120H1 Full Course Notes
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Short term survival of cell depends on preventing changes in dna (environmental radiation, chemicals) Longterm survival of species requires dna sequences to be changeable over many generation. Cells want to remain same, but selection pressures force evolution. Def of mutation rate: the rate at which observable changes occur in dna sequences. How are they measured: directly from experiments carried out. Example is e. coli, which divides once every 40 min producing billions of cells in one day. When looking at all of those cells, it is easy to identify the small fration of the bacteria that have suffered the mutation in a particular gene. Hard to tell actual mutation rate as mutations can be silent, so only really the deadly mutations are viewable. Rate: bacteria display a mutation rate of about 1 nucleotide change per 109 nucleotides per cell generation. C elegans example: generation time is 4 days.