Chapter 23 SG - Chapter 23 Microevolution- small-scale...

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Chapter 23 Microevolution- small-scale evolutionary change of genotype of a population from generation to next; analysis of one pop’s gene pool Modern Synthesis- evolutionary theory that integrates ideas from many other fields of science (i.e. paleontology, biology, etc.) Population- localized group of individuals that can interbreed and produce fertile offspring Gene Pool- hypothetical “pool” of the entire population’s genes Fixed Allele- allele that is alone at a particular locus (only 1 allele at specific locus); 2 or more alleles at locus hetero or homozygous Hardy-Weinberg Theorem- frequencies of alleles and genotypes in a pop’s gene pool remain constant from generation to next a. Used only for non-evolving populations; done only when Mendelian segregation and allele recombination occur b. Preserves genetic variation from one generation to the next in populations not evolving Hardy-Weinberg Equilibrium- results from H-W theorem where population will have same allele freq. that determines genotype freq. a. Uses the formula p 2 + 2pq + q 2 =1 , where p 2 is homozygous dominant, q 2 is recessive, and 2pq is heterozygous b. 5 conditions must be met for non-evolution to occur (H-W Equilibrium) 1. Extremely Large Population- allows fewer chances of genetic drift , or allele frequency fluctuations due to small pop 2. No Gene Flow- no emigration from or immigration to the gene pool of population that may otherwise change freq. 3. No Mutations- no further modification of pre-existing genes that could once again alter allele freq. 4. Random Mating- no selective (i.e. inbreeding) permitted, allowing random mixing of gametes within the population 5. No Natural Selection- if nature favors certain traits, certain alleles will die off, altering pool’s allelic freq. Mutations- only affects gene pool (H-W Equlibrium) when reproductive cells (gametes) are mutated and thus pass on mutations Point Mutations- mostly harmless due to the majority of non-coding DNA of eukaryotic genome (redundant genetic code) Harmful Mutations- delete, disrupt, or rearrange chromosome; rare cases, these may be beneficial Duplication- important source of genetic variation; transposable elements
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This note was uploaded on 08/27/2010 for the course BIO 8432 taught by Professor Lang during the Spring '10 term at Northwestern IA.

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Chapter 23 SG - Chapter 23 Microevolution- small-scale...

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