PREFACE 



Part of a letter by G. Mendel and the Nobel 

 Prize Lectures presented by geneticists are 

 included in the book as Supplements. These 

 Supplements should be completely under- 

 standable, or nearly so, if the appropriate 

 Chapters preceding them have been read, 

 and can serve as a review and overview of 

 genetic principles and their applications. 

 The Supplements can also function to bridge 

 the gap between the textbook and the re- 

 search worker, giving the reader some idea 

 of the history of the subject and the person- 

 alities of the people involved. 



In certain cases it has been considered 

 desirable in the present work to combine 

 the results, obtained by different people at 

 different times using different organisms and 

 methods, into a single organized body of 

 information, rather than to try to prove a 

 principle or illustrate an application using a 

 patchwork of evidences in which each worker 

 is given his due priority. Since the later 

 Chapters deal with recent advances in ge- 

 netics, whose discussion may be absent from 

 already published textbooks, additional in- 

 formation can be gained from reading the 

 original scientific literature. Accordingly, 

 more references are given to particular work- 

 ers in the later than in the earlier Chapters. 

 The citations to the literature included in 

 the Nobel Prize talks should prove especially 

 valuable to those who wish to do additional 

 reading on key topics. 



It is hoped that the student will benefit, 

 whatever his future course of study, from 

 the numerous opportunities this text provides 

 for him to think scientifically — to study the 

 design of experiments, to analyze the infor- 

 mation these provide, and to reach valid 

 conclusions. Because a genetics course is 

 elected more and more frequently by students 

 who do not wish to specialize in biology and 

 because it should be no longer a course 

 only for upper classmen, I have tried to 

 use simple biological examples and termi- 

 nology whenever possible, and have explained 



in some detail certain biological phenomena 

 generally understood by students specializing 

 in biology. Because many students in a first 

 course in genetics are deficient in training in 

 chemistry and physics I have also explained 

 certain aspects of these sciences, important 

 for understanding genes and their behavior, 

 in somewhat more detail than is found in 

 the usual text. On the other hand, since 

 elaborate statistical analysis is needed usually 

 only to demonstrate certain complex appli- 

 cations of genetic principles, the mathematics 

 of genetics has been de-emphasized here, 

 leaving it to the individual instructor to 

 elaborate upon, as he sees fit, in the lecture 

 and laboratory periods. 



Questions and problems are presented after 

 each Chapter. Instructors or students who 

 would like to have additional discussion and 

 examination questions covering much of the 

 material in this book as well as reading assign- 

 ments in other basic textbooks can find these 

 in the Study Guide and Workbook for Genetics 

 (McGraw-Hill Book Co., Inc., 1960) which 

 I prepared. 



Finally, it should be emphasized that be- 

 cause this textbook of genetics has been pre- 

 pared by a fellow human being it therefore 

 has certain limitations. This book or any 

 other text is subject to a very personal factor 

 in that the author has selected certain infor- 

 mation for presentation and rejected other 

 material considered less essential. Moreover, 

 while each author does the best he can with 

 the knowledge available, what is accepted by 

 him one day is quickly subject to improvement 

 or rejection by him consequent to the dis- 

 coveries of the next day. To foster these im- 

 pressions the present work is written, as much 

 as possible, as a personal discussion between 

 you and me; it is aimed to help you think 

 critically, to challenge the experimental evi- 

 dence I have presented, the reasoning I have 

 used in its evaluation, and the conclusions I 

 have arrived at. You are cordially invited 

 to play this thinking game with me. But 



