Heredity - 519 



b. heterozygous normal mother and color- 

 blind father 



c. heterozygous normal mother and nor- 36. 

 mal father 



31. Enumerate the problems that have made it 

 difficult to analyze the details of human 

 heredity. 



32. If each phenotypic characteristic of the or- 

 ganism is determined by several or many 

 pairs of genes, how is it possible that simple 

 ratios (for example, 3:1 and 1:2:1) are ob- 

 tained in the F 2 generation when the inheri- 37. 

 tance of a particular characteristic is stud- 

 ied? 



33. Define the term population genetics. Illus- 

 trate this explanation with reference to Sny- 

 der's study of the inheritance of "tasting 

 capacity." 



34. Who coined the phrase "inborn errors of 

 metabolism"? Give three examples oi this 38. 

 phenomenon. Explain how and why a study 



of these metabolic defects lends support to 

 the "one gene, one enzyme" hypothesis (p. 

 529). 



35. What difficulties were encountered in de- 

 termining the exact chromosome complement 

 of man? Explain how these difficulties were 

 surmounted. Explain how certain chromo- 



somal aberrations arc related to certain grave 

 pathological situations. 



Discuss the phenomena of mutation, accord- 

 ing to the following topics: 



a. definition of the process 



b. types of mutation 



c. frequency of the types 



d. factors that may modify the frequency 



e. proof that a mutation cannot represent 

 the mere loss or destruction of a gene 



f. relation of mutations to evolution 

 Carefully differentiate between the members 

 of each pair of terms: 



a. genetic and environmental variation 



b. an aberration and a true mutation 



c. a deficiency and a duplication 



d. translocation and inversion 



e. triploidy and tetraploidy 



f. artificial and natural selection 

 Discuss the problems of selective breeding, 

 emphasizing particularly: 



a. the general technique 



b. relation between inbreeding and homo- 

 zygosity 



c. the dangers of inbreeding and how 

 these may be overcome 



d. the practical value of the method 



e. the limitations of selective breeding 



FURTHER READINGS 



1. You and Heredity, by Amram Scheinfeld; 

 New York, 1950. 



2. Multiple Human Births: Twins, Triplets, 

 Quadruplets, and Quintuplets, by H. H. New- 

 man; New York, 1940. 



3. Science in Progress, chapter by G. W. Beadle; 

 New Haven. 1949. 



4. Principles of Human Genetics, by C. Stern; 

 San Francisco, 1960. 



5. Genetics in the 20th Century, L. C. Dunn, 

 editor; New York, 1951. 



6. "The Chemistry of Hereditary Disease," by 

 A. G. Beam; in Scientific American, Decem- 

 ber 1956. 



7. "Chromosomes and Disease," by A. G. Beam 

 and J. L. German III; in Scientific American, 

 November 1961. 



