718 General and Applied Biology 



the period of procreation. Surveys show that sterilization is satisfactory 

 to those sterilized and to society in general, and the cost is much less 

 than the more expensive care and treatment of great numbers, either in 

 or outside of institutions. (3) By methods of birth control, or the spac- 

 ing of the birth of children and the regulation of their number com- 

 mensurate with the abilities of the parents to care and train them prop- 

 erly. (4) By methods of contraception whereby fertilization may be 

 prevented, although this method will probably be of least benefit to those 

 groups who need it most — morons, imbeciles, idiots, etc. About 5 per 

 cent of the people of the United States have an inteUigence quotient 

 (I.Q.) of 70 or less. It is up to the people of our country to decide what 

 action is to be taken, but whatever action is taken should be in the light 

 of scientific knowledge so that the results will be what are expected 

 and desirable. 



QUESTIONS AND TOPICS 



1. Define genetics in your own words. 



2. Discuss each of the methods used in the study of genetics. For what particu- 

 lar type of investigation is each method fitted? 



3. Which method is best fitted for the study of human genetics? Discuss the 

 reasons why certain methods cannot be used practically in human genetics. 



4. Discuss reasons why the study of human genetics apparently has not reached 

 the high level that has been attained in genetic studies of plants and lower 

 animals. 



5. What is the relationship between the study of genetics and a study of varia- 

 tions? What is the relationship between genetics and the general principles 

 of evolution? How can genetics assist in solving problems in these two fields? 



6. In what ways can hybridization of animals and plants be of practical value? 

 List several specific examples to prove your points. 



7. Discuss the properties of genes and genie action. 



8. Discuss multiple genes and the interaction of genes, describing each type and 

 giving an example of each. 



9. Describe chromosomes, giving their outstanding characters. Do closely related 

 animals or plants necessarily have identical or similar numbers of chromosomes? 

 Give examples to prove your point. 



10. Giv^e all the evidence you can for believing that inheritance of detailed struc- 

 tures is due to chromatin rather than to other parts of the cell. 



11. State and illustrate the laws of Mendelism. 



12. Define (1) hybrid, (2) heterozygous, (3) homozygous, (4) dominant, (5) 

 recessive, (6) phenotypc ratio, (7) genotype ratio, (8) allele. 



13. Explain what is meant by a monohybrid cross; by a dihybrid; by a trihybrid. 



14. What is the value of the Punnet square or checkerboard in determining 

 heredity? 



