Lec16_PP_S11 - Important Equations: L ectu re 1 6 : N a t u...

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Lecture 16: Natural Selection (Part 2) Important Equations : Mean Fitness : w = p 2 w AA + 2pqw Aa + q 2 w aa Mean Allele Fitnesses : w A = pw AA + qw Aa w a = pw Aa + qw aa q and Δ q : q’ = q( w a / w) Δ q = [pq( w a - w A )]/ w An Example : p = 0.3 and q = 0.7 Allele a is recessive and deleterious: w aa = 0.6 What is q’? w = p 2 w AA + 2pqw Aa + q 2 w aa = (0.3) 2 (1) + 2(0.3)(0.7)(1) + (0.7) 2 (0.6) = 0.09 + 0.42 + 0.29 = 0.80 w a = pw Aa + qw aa = (0.3) + (0.7)(0.6) = 0.72 An Example : Therefore, q’ = q( w a / w ) q’ = (0.7)(0.72/0.8) = 0.63 Allele a has decreased in frequency in one generation from 0.70 to 0.63 due to selection.
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Models of Selection : Models of Selection : 1. Selection against a recessive. 2. Selection against a dominant 3. Selection for the heterozygote. 4. Partial Dominance 5. Underdominance Models of Selection : Genotype Fitness Type of Selection AA Aa aa Against a recessive 1 1 1-s aa Against a dominant 1 -s AA 1 - s Aa 1 For heterozygote 1 - s AA 1 1 - s aa Partial Dominance 1 1-0.5s aa 1-s aa Underdominance 1 1-s 1 Selection Against A Recessive : Mean Fitness : w = p 2 w AA + 2pqw Aa + q 2 w aa = p 2 + 2pq + q 2 (1 - s) = p 2 + 2pq + q 2 - sq 2 = 1 - sq 2 Mean Allele Fitness : w a = pw Aa + qw aa = p + q ! (1 -s) = p + q - sq = 1 - sq w A = pw Aa + qw
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This note was uploaded on 05/07/2011 for the course BIOLOGY 352 taught by Professor Townsend during the Spring '08 term at San Diego State.

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Lec16_PP_S11 - Important Equations: L ectu re 1 6 : N a t u...

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