Evolution Notes: Week Six
Evolution Notes: Week Six BIO318
Virginia Commonwealth University
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This 4 page Class Notes was uploaded by Jayda Abrams on Sunday October 9, 2016. The Class Notes belongs to BIO318 at Virginia Commonwealth University taught by Dr. Turbeville in Fall 2016. Since its upload, it has received 7 views. For similar materials see Biology: Evolution and Biodiversity in Biology at Virginia Commonwealth University.
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Date Created: 10/09/16
Week Six Tuesday 10/4/16 D can be positive, negative or equal to zero. D= 0 = linkage equilibrium D= - = observed is lower than the expected D= + = observed is more than the expected Linkage disequilibrium can be generated by several processes: 1. Physical linkage 2. Mutation 3. Natural selection 4. Migration 5. Genetic drift Physical- closer together = more likely to be in linkage disequilibrium. Recombination takes away linkage disequilibrium. It is the only thing that will take it away. Why does it take it away? Recombination is the mixing of alleles and crossing over occurs. Alleles on one chromosome combine with a homolog. When you start crossing over it makes the alleles independent. Mutation- Mutation occurs on 1 haploid and creates a non-independent. Selection- Avoiding certain haplotypes because they are not advantageous. This means they are no longer independent. Migration- Bring haplotypes to another environment (how to figure out where people came from and moved from). Genetic drift- Random fixation or loss of alleles. Haplotypes are lost by random chance and it creates a non-independence. Phenotypes and genotypes Heritability- measure of proportion of phenotypic variance explained by genetic drift. It ranges from 0 to 1. 0 being no genes determine the value, 1 meaning all. 2 Heritability is H . When doing this you do not solve for H. It is squared because you are solving for a type of variance. Additive genetic effects = h = narrow sense heritability. What is the differences between narrow and broad sense? Dominance and epistasis is ignored. Response to Selection Breeder’s equation is used to maximize profits and to make predictions. S is also equal to the parent generation after selection minus the parent generation before selection. Does this actually work? Yes! If S doesn’t change h does. h is population and time specific. When the population changes so does the heritability. This is because it is based on alleles that have frequencies. Drift will make the heritability go to zero. Heritability is based on two alleles. Loss of alleles and loss of variability makes heritability go to zero. There must be variance to have heritability. Heritability and inheritance are not synonyms. Why? Heritability needs variance and inheritance is just the passing of traits from one generation to the next.