1. Population Genetics: An introduction Change in Populations & Communities: Population Genetics

2. Major topics & questions in Unit 4: Change in Populations & Communities: Population Genetics 1.Populations can be described in terms of gene pools: What kinds of events can change a gene pool? Can we measures changes in a gene pool? What happens to native gene pools if we introduce an exotic species into an ecosystem? 2.Populations interact with each other: What kind of relationships exist in ecosystems (Biology 20 review)

3. Major topics & questions in Unit 4: Change in Populations & Communities: Population Genetics 2.Populations grow in characteristic ways: What factors influence population growth? How does chaos theory affect population growth?

4. Change in Populations & Communities: Population Genetics Community Population Species Gene Mutation Allele Gene Pool Random change in DNA All genes in a specific population Members of 1 species within a certain area & time Segment of DNA that codes for a protein All populations that interact with each other Individuals that can mate & produce viable offspring Alternative form of a gene

5. Pause for Math Review Change in Populations & Communities: Population Genetics Convert the following percentages to decimals: 42% = 9% =

6. Hardy – Weinberg Principle Change in Populations & Communities: Population Genetics We can measure the allele frequency of genes in a given population using the Hardy-Weinberg principle. The principle predicts that if all factors remain constant, the gene pool will have the same composition of alleles generation after generation. This stability of the gene pool is called genetic equilibrium.

7. Hardy – Weinberg Principle Change in Populations & Communities: Population Genetics Notice that the equation applies to an idealized population that is not evolving. Conditions where no change (evolution) occurs: 1.Large populations ( to reduce effect of chance) 2.Random mating 3.No mutations 4.No immigration or emigration 5.No selection (all genotypes reproduce equally)

8. Change in Populations & Communities: Population Genetics If a population is not evolving, the frequency of alleles will remain the same from generation to generation and can be predicted as follows: Where p = frequency of allele A q = frequency of allele a Note: p + q = 1 p 2 + 2pq + q 2 = 1

9. Change in Populations & Communities: Population Genetics The formula shows the frequency of alleles as they appear in the genotypes in an entire population. Example – What are genotype frequencies in a population for alleles A and a if the frequency of allele A is 0.7. Step 1: p 2 + 2pq + q 2 = 1 ( ) 2 + ( ) + ( ) 2 = 1 ( ) + ( ) + ( ) = 1 P = frequency of allele A = 0.7 1-p = q 1-0.7 = 0.3 q = frequency of allele a = 0.3 Step 2:

10. Change in Populations & Communities: Population Genetics The formula shows the frequency of alleles as they appear in the genotypes in an entire population. p 2 + 2pq + q 2 = 1 A 2 + 2Aa + a 2 = 1 ( ) 2 + ( ) + ( ) 2 = 1 ( ) + ( ) + ( ) = 1 Frequency of allele A = 0.7 Frequency of allele a = 0.3 (p + q = 1; 0.7 + 0.3 = 1) A (0.7)a (0.3) A (0.7) a (0.3)

11. Change in Populations & Communities: Population Genetics Example 1: A recessive genetic disorder occurs in 9% of the population. What percentage of the population are carriers, but do not have the disorder?

12. Change in Populations & Communities: Population Genetics Example 2: For a moth population 60% of moths are white (dominant) and 40% are black. Three years later 65% of moths are white and 35% are black. What is the change in allele frequencies for W and w.

13. Change in Populations & Communities: Population Genetics Challenge: