LEQ: How has knowledge of genetics influenced modern ideas about evolution?

1. LEQ: How has knowledge of genetics influenced modern ideas about evolution? 13.6 to 13.8

2. Populations are units of evolution • A group of interacting individuals belonging to one species and living in the same geographic area • A group whose members possess similar anatomical characteristics and have the ability to interbreed Population Species

3. Populations are units of evolution • The study of genetic changes in populations; the science of microevolutionary changes in a population • A comprehensive theory of evolution that incorporates genetics and includes most of Darwin’s original ideas, focusing on populations as the fundamental units of evolution (individuals don’t evolve – populations do) Population Genetics Modern Synthesis

4. Populations are the units of evolution • All of the alleles for all of the loci in all individuals in a population • Each allele has a frequency in the population • Example: you have a wild boar population in which 50 percent of the alleles for a particular gene are dominant (B) and 50 percent of the alleles for the gene are recessive (b). Gene Pool Example

5. Populations are units of evolution • A change in a populations gene pool over a succession of generations; evolutionary changes in species over relatively brief periods of geologic time • Change in the allele frequency over time Microevolution example

6. The gene pool of nonevolving populations remains constant… • Named for 2 men who figured out that the shuffling of genes that occurs during sexual reproduction, by itself, cannot change the overall genetic make-up of a population • p + q = 1 (p = dominant allele frequency / q = recessive allele frequency) • p2 + 2pq + q2 = 1 ( p2 = homo dominant; 2pq = hetero; q2 = homo recessive) • Large population • No migration in or out • Mutations do not alter gene pool • Random mating • Natural selections does not occur (all have equal chance to survive) Hardy Weinberg Equilibrium 5 Conditions of Hardy Weinberg

7. Hardy Weinberg equation is useful in public health science • About 1 in 10,000 babies born in the US have PKU • How many people are carriers? • First step: calculate q2 (individuals with PKU / homo recessive) • q2 = 1/10,000 = 0.0001 • Solve for q (the frequency of the recessive allele in the population) • q = q2 = 0.01 • Use the equation “p + q = 1” to solve for p. • p = 0.99 • Use the equation “p2 + 2pq + q2 = 1” and solve for carrier genotype. • 2pq = 2(.99)(.01) = .0198 • ~2% of the population are carriers PKU – autosomal recessive trait

8. Example #2 • You have sampled a population in which you know that the percentage of the homozygous recessive genotype (aa) is 36%. Using that 36%, calculate the following: • The frequency of the "aa" genotype. • The frequency of the "a" allele. • The frequency of the "A" allele. • The frequencies of the genotypes "AA" and "Aa." • The frequencies of the two possible phenotypes if "A" is completely dominant over "a." • q2 = .36 • q = .6; frequency of “a” allele is 60% • p = .4; frequency of “A” allele is 40% • p2= .16; frequency of AA is 16% • 2pq = .48; frequency of Aa is 48% • Frequency of A phenotype is 64% • Frequency of a phenotype is 36% Try it yourself Answer