1 BIO 201 GENETICS Lecture #20 “Population Genetics & Conservation Biology” Dr. Karen Schmeichel October 17, 2008

2 Business Items: An apology Lab on 10/20 Meet in G 229 first! Virtual PCR Lab & Fly Lab Meeting Hb lab write-up due Next Notebook collection (leave out virtual Lab) Mid-term heads up Genetics and Society papers due 10/31

3 Objectives: Understand that alleles in populations can be tracked and quantitated via mathematical expressions Explain Hardy-Weinberg Equilibrium as a model for undisturbed populations Consider H-W assumptions Use Prairie Chickens and Orchids as examples of how destabilizing H-W can lead to decreased genetic diversity/extinction

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5 2 Fundamental Calculations: Genotype Frequencies Allele Frequencies

6 # Individuals with a particular genotype in a population Genotypic Frequency Total # individuals in a population

Fig Genotype Frequency in Scarlet Tiger Moths BB Bb bb

8 # copies of an allele in a population Allele Frequency Total # of all alleles for that gene in a population

9 In a Population of 1,000 diploid individuals 353 AA 494 Aa 153 aa Calculate the Allele frequencies (“p” & “q”).

10 In a given population with alleles A and a: p + q = 1

11 Hardy-Weinberg Equilibrium: Describes how allele and gentype frequencies do not change of the course of many generations, unless destabilizing conditions exist p 2 +2pq + q 2 = 1 f(AA)f(Aa)f(aa)

Fig. 24.3: HW Equilibrium is Predictive

If p = 0.8, what are the frequencies of AA, Aa and aa in a population that is in H-W Equilibrium?

= 0.8= 0.2 = 0.8 = 0.2 = 0.8 x 0.8 = 0.8 x 0.2 = 0.2 x 0.2 f(AA) =.64 f(Aa) =.32 f (aa) =.04 Another Way to conceptualize HW:

Can Use HW to Predict Heterozygotes (Carriers) Cystic Fibrosis Occurs in 1/2,500 Individuals. Calculate the Frequency of CF Carriers.

Hardy Weinberg Conditions: Allele and genotype frequencies will not change from generation to generation if: 1.No new mutation 2.No genetic drift 3.No migration 4.No natural selection 5.No random mating

Illinois Prairie Chicken: How is H/W Destabilized?

18 Effects from Small Pop. Prone To Environmental Disasters? Effects from Inbreeding Depression?

19 F= Inbreeding Coefficient Issues of Non-Random Mating

20 Take-Home Points: Population genetics is the study of allele relationships in whole populations The Hardy Weinberg Equilibrium is a mathematical expression describing the relationship between genotypic frequencies and allele frequencies in a given population that is at equilibrium Equilibrium can be disrupted by mutation, genetic drift, migration, natural selection and non-random mating Conservation efforts focus largely on maintaining optimal genetic diversity (e.g., reducing effects of inbreeding) in a population

21 Assignments: Quiz Material (for 10/20): Ch 15: (Ch 6: ) & Ch 16: (Ch 7: ) Problems: Ch 24: 23, 33, 34 & 37 (same in “Mendelian”)