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November 27.doc

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Department
Biology (Sci)
Course
BIOL 111
Professor
Multiple
Semester
Fall

Description
Bio 111 Alanna Houston November 27, 2007 Mutations: - Mutations are the ultimate source of all genetic variation. Mutations change the genetic code which generates new alleles which may change amino aid sequences which may have phenotypic effects - Examples of mutations with phenotypic effects in Drosophila: - - Most mutations decrease fitness (i.e. survival and reproductive success) and are considered deleterious - The average mutation reduces fitness by about 2% - The few beneficial mutations are likely to be of small effect (hopeful monsters are rare) Genetic Drift: - Causes random changes in allele frequency Bio 111 Alanna Houston - - Stronger in smaller populations: allele frequencies in computer simulations - - In the lab: o 107 populations of fruit fly o Each generation founded by eight males and eight females o Two selectively neutral eye colour alleles o Allele frequencies = 0.5 in all populations in the generation zero Bio 111 Alanna Houston o Natural Selection: - Wallace and Darwin - All organisms have the potential for exponential growth – and yet most populations remain relatively stable in the number of individuals - This implies high mortality in nature - Traits vary among individuals - Traits influence survival - Traits are heritable - Prediction: traits that improve survival should increase in frequency (or size) through time - Darwin used domestic breeds as an example of the power of selection (birds) - The power of selection is also seen in
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