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Population Genetics

Population Genetics. Unit 5 – Lecture 4. Darwin’s Five Points. Observations regarding natural selection: populations have variations some variations are beneficial / favorable more offspring are produced than survive those that survive will have favorable traits

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Population Genetics

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  1. Population Genetics Unit 5 – Lecture 4

  2. Darwin’s Five Points • Observations regarding natural selection: • populations have variations • some variations are beneficial / favorable • more offspring are produced than survive • those that survive will have favorable traits • because of this, a population will change over time

  3. Genetic Equilibrium • Recall – natural selection affects POPULATIONS not individuals • Gene Pool – the collection of genes within a population • allelic frequency – the frequency of certain alleles within a population

  4. Genetic Equilibrium – cont’d • Genetic Equilibrium – a steady-state of genetic material/information within a population • no new traits added, none removed • doesn’t really happen in nature [will discuss why soon]

  5. Genetic Equilibrium – cont’d • Hardy-Weinburg Law • can find out how many alleles are in population if you assume that there is genetic equilibrium at any single point in time

  6. Discuss • List and explain Darwin’s Five Points. • Name and explain reasons why genetic equilibriumdoes NOT exist in nature.

  7. Genetic Equilibrium – cont’d • Genetic Equilibrium could be achieved if: • there is a large breeding population • no selection • all traits must be as favorable than others to maintain the same amounts of each allele • random mating exists • if there is sexual selection, certain traits would be favorable…which would change the amounts of each allele in the population

  8. Genetic Equilibrium – cont’d • Genetic Equilibrium could be achieved if: • no change due to mutations • any loss or gain of alleles would change the genetic ratios • no immigration or emigration • when organisms leave, they take with them their traits • when organisms arrive, they bring in new traits

  9. Genetic Equilibrium – cont’d • Genetic Equilibrium does not exist because of… • selection • natural or otherwise – changes amount of certain genes • mutation • loss or gain of info – changes amount of certain genes • gene flow • emigration / immigration

  10. Genetic Equilibrium – cont’d • Genetic Equilibrium does not exist because of… • genetic drift • small populations exist in which certain genes are more prevalent than in the general populus • American Indians do not have blood group B • Amish – marry within their own community, so more likely to have certain recessive conditions likepolydactyly [extra fingers]

  11. Genetic Equilibrium – cont’d • Genetic Equilibrium does not exist because of… • natural disasters / mass illness • cause the “bottleneck” effect

  12. Discuss • Again, summarize the reasonswhy genetic equilibrium does NOT exist in nature.

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