Some principles of genetics
Although the application of hereditary principles to the development of various varieties of domesticated plants and animals goes back into prehistory, a comprehensive theory of inheritance is the product of the twentieth century ( Dunn, 1951). Present-day genetics represents the fusion of two lines of investigation, one dealing with the processes of cell division and fertilization, the other concerned with crossing variant types and analyzing the characteristics of the offspring by statistical methods.
The following pages contain an elementary account of selected topics in genetics for individuals without formal training in this area or for those who have lost contact with a science which is constantly adding to its factual and theoretical foundations. Readers who are acquainted with the science may omit this chapter and portions of Chapters 3 and 4 without disrupting the continuity of the discussion. Modern advances in such fields as physiological genetics, selection theory, and the genetics of quantitative characters have special significance for the student of the behavioral sciences. To a great extent these concepts have been under-represented in elementary biology courses. Perhaps the predilection of some investigators for simple genetic models to explain complex behavioral characters is due to unfamiliarity with more complex systems. And perhaps some anti- heredity bias stems from the realization that single-gene models are inadequate, as well as from a lack of acquaintance with other concepts.
Major areas of genetics which have only a peripheral relationship to behavior have been omitted in this brief summary. Obviously our choice is arbitrary, and those who are stimulated to seek a more complete account are advised to find it in one of several excellent general or specialized textbooks. (For example, Srb and Owen, 1953;