1. HS-LS-3 Apply concepts of statistics and probability to support explanations that organisms with an advantageous heritable trait tend to increase in proportion to organisms lacking this trait

2. Population Genetics Definition - the study of evolutionary forces that act on a population and the genetic variability within that population. Evolution occurs on a POPULATION level – An individual is ONE single organism of a particular species living in a particular place at a given time – A population is ALL of the organisms of a particular species living in a particular place at a given time.

3. Population Genetics – Some Important Terms Gene – a DNA segment that codes for a particular characteristic. Allele – an alternate form of a gene (can be 2 or more). Locus (pl. = loci) – the position on a chromosome where an allele is found. http://www.cell-research.com/20034/pic01/Fig%203.gif Homologous Chromosomes Locus Alleles

4. Population Genetics – More Important Terms Phenotype – Dominant – the expressed characteristic – Recessive – the hidden characteristic Homozygous vs. heterozygous genotype http://blog.scs.sk.ca/bwapple/2012/03/ http://dartmed.dartmouth.edu/spring10/html/ moore.php

5. Population Genetics – Even More Important Terms Analyzing the phenotype of a heterozygote – Complete dominance – one member of the pair of alleles is expressed and the other is hidden – Co-dominance - the traits from both alleles are expressed – Incomplete dominance– the trait is an intermediate of the 2 alleles

6. Understanding the Evolution of a Population Genetic equilibrium – a state where the population’s allele and genotype frequencies do not change from one generation to the next. Allele frequency = the proportion of a specific allele in a population (i.e. A vs a) Genotype frequency = the proportion of a particular genotype in a population (i.e. AA vs Aa vs aa) Phenotype frequency = the proportion of a particular phenotype in a population (i.e. dominant vs recessive)

7. Hardy-Weinberg Principle and Population Genetics Describes populations at genetic equilibrium In the absence of evolutionary influences, the frequency of alleles and genotypes in a population will remain unchanged. – Population MUST be large – No mutations – Mating must be random – No natural selection – No gene flow Interest lies in determining the frequency of alleles or genotypes in a population. It is important to evaluate actual versus expected!

8. Hardy-Weinberg Principle and Population Genetics Animation = http://www.youtube.com/watch?v=T6KkEMSEyvohttp://www.youtube.com/watch?v=T6KkEMSEyvo

9. Hardy-Weinberg Principle and Population Genetics Calculating allele frequency based on phenotypes – i.e. 500 wildflower plants: 320 of which are red (C R C R ), 160 have pink flowers (C R C W ), and 20 with white flowers (C W C W ). Diploid organisms C R allele – (320*2 + 160)/1000 or 800/1000 = 0.80 C w allele – (160+20*2)/1000 or 200/1000 = 0.20 Calculating allele frequency using Hardy-Weinberg – p = frequency of dominant allele (i.e. A) – q = frequency of recessive allele (i.e. a) p + q = 1

10. Hardy-Weinberg Principle and Population Genetics Calculating genotype frequencies based on observed phenotypes i.e. 500 wildflower plants: 320 of which are red (C R C R ), 160 have pink flowers (C R C W ), and 20 with white flowers (C W C W ). – 320/500 = 0.64 – 160/500 = 0.32 – 20/500 = 0.04 Calculating the genotype frequency using Hardy-Weinberg – A genotype is 2 alleles Allele 1 AND Allele 2 – For allele 1, p+q = 1 – For allele 2, p+q=1 – SO … (p+q)(p+q)=1 p 2 + 2pq + q 2 = 1 – p 2 = the frequency of AA – 2pq = the frequency of Aa – q 2 = the frequency of aa

11. Hardy-Weinberg Principle and Population Genetics Let’s watch a few examples. http://www.youtube.com/watch?v=oG7ob-MtO8c Note: start video at 7 minutes in!