228 CHAPTER 26 



Rasmuson, M., Genetics on the Population Level, Stockholm, Sweden, Svenska Bokforlaget 

 Bonniers; London, Heinemann, 1961. 



Weinberg, W., "Uber den Nachweiss des Vererbung beim Menschen," Jahresh. Verein f. 

 vaterl. Naturk. in Wurttemberg, 64:368-382, 1908. Translated, in part, in Stern, C, 

 "The Hardy-Weinberg Law," Science, 97:137-138, 1943. 



QUESTIONS FOR DISCUSSION 



26.1. Does evolution have the same causes in populations reproducing only asexually, as 

 in those reproducing sexually? Explain. 



26.2. Suppose, in a population obeying the Hardy-Weinberg rule, mutation occurred for 

 one generation, thereby changing the composition of the gene pool. How many 

 additional generations would be required before a new genetic equilibrium would be 

 established? Explain. 



26.3. Discuss the statement: "The Hardy-Weinberg Law is the cornerstone of evolutionary 

 genetics." 



26.4. Assuming the Hardy-Weinberg principle obtains, what is the frequency of the gene R, 

 if its only allele R' is homozygous in the following percentage of individuals in the 

 population: 49%? 4%? 25^^70? 36%? 



26.5. About 70% of Americans get a bitter taste from the drug phenyl thiocarbamide (PTC), 

 and are called "tasters." The remaining 30% of the people get no bitter taste from 

 PTC, and are "nontasters." 



All marriages between nontasters produce all nontaster offspring. All results 

 support the view that a single pair of nonsex-linked genes determines the difference 

 between tasters and nontasters, that dominance is complete between the only two 

 kinds of alleles that occur, and that penetrance of the dominant allele is complete. 



a. Which of the two alleles is the dominant one? 



b. What proportion of all marriages between tasters and nontasters have 

 no chance (barring mutation) of producing a nontaster child? 



c. What proportion of all marriages occurs between nontasters? tasters? 



26.6. The proportion of A A individuals in a large crossbreeding population is .09. Assuming 

 all genotypes with respect to this locus have the same reproductive potential, what 

 proportion of the population should be heterozygous for Al 



26.7. What do you suppose would happen to a population whose gene pool obeyed the 

 Hardy-Weinberg rule for a very large number of generations? Why? 



26.8. Can the same population obey the Hardy-Weinberg rule for one locus and not for 

 another? Explain, 



