[PDF] allele frequencies, Hardy-Weinberg, and haploid selection models

7036_3practice1x.pdf Practice problems: allele frequencies, Hardy-Weinberg, and haploid selection models An answer key will be posted, but don't be tempted to peak before doing your work! I. Basic level (Exam questions will be more challenging) A. Red and white are codominant in four o'clocks (Mirabilis). A population consists of 35 red plants, 54 pink plants, and 67 white plants. Calculate the genotype and allele frequencies. Is this population in Hardy-Weinberg equilibrium? Show your work. B. A recent field experiment examined how the genotype at one locus affected the survival of sunflowers. 200 individuals with the AA, Aa, and aa genotypes were planted. Survival was surveyed at the time of flowering. AA Aa aa number surviving 170 20 20 What are the relative fitnesses and selection coefficients for each genotype? II. Intermediate level: exam questions will often be at roughly this level of difficulty. C. Explain the difference between absolute and relative fitness, and why relative fitness is more useful for explaining evolution. D.. One locus is expressed only in Drosophila sperm and not at any other point in the life cycle, with one allele having fitness higher than the other. The relative fitness for allele A is 1.0, and for allele a is 0.8. i. Suggest one way to experimentally determine the fitness of fruit fly sperm. ii. If the initial frequency of allele A is 0.1, sketch the change in allele frequencies over the next 50 generations. (No calculations needed, only general shape.) iii. At what allele frequencies is the curve steepest? Explain why making use of the equations of haploid selection model. iv. How would this curve differ if the relative fitness for allele a were 0.9 rather than 0.8? E. Explain the logic behind the equation for the frequency of allele A after selection: aAA

WtqWtpWtptp)()()()1(

III. Advanced level: most exam questions will not be this difficult. F. Use calculus to demonstrate that the maximum rate of allele frequency change will occur when p = 0.5. G. If allele A changes in frequency from 0.2 to 0.8 in 50 generations, what is the selection coefficient for allele a?