VI 



PREFACE 



Ing different degrees of sophistication are 

 given at the ends of chapters. Since the later 



chapters deal with recent advances in genet- 

 ics, whose discussion may be absent from 

 already published textbooks, more references 

 are given to particular workers in the later 

 than in the earlier chapters. 



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 un- 

 derstandable, or nearly so. if appropriate 

 chapters have been read beforehand, and can 

 serve as a review and overview of genetic 

 principles and their applications. The cita- 

 tions to the literature included in the Nobel 

 Prize talks should prove especially valuable 

 to those who wish to do additional reading 

 on key topics. The supplements can also 

 function to bridge the gap between the text- 

 book and the research worker, giving the 

 reader some idea of the history of the subject 

 and the personalities of the people involved. 



The Second Edition 



The subject matter is presented in forty-two 

 chapters, each ending, as before, with a sum- 

 mary, questions for discussion, and refer- 

 ences. An appendix. "Elementary Biomet- 

 rical Inferences," has been added, and the 

 supplements now include three additional 

 Nobel Prize lectures. A description of rep- 

 resentative life cycles and genetic maps of 

 several higher organisms have also been 

 added. Recent advances — for example, in 

 human, corn, and Drosophila genetics and in 



our understanding of the genetic code and 

 the regulation of gene synthesis and gene 

 action — have required that several chapters 

 be combined or rearranged in sequence and 

 that new chapters be written. Additional fig- 

 ures, photographs, problems, and references 

 are also included. 



Suggestions for Use of the Book 



The text contains more information than is 

 usually covered in a one-semester, introduc- 

 tory course for undergraduates. The chap- 

 ters or chapter sections that are marked by 

 an asterisk do not contain principles or 

 terminology needed to understand unmarked 

 parts and are, therefore, optional. 



A one-semester lecture course (meeting 

 about 30 to 45 periods) can be based upon 

 ( 1 ) thirty chapters — those whose chapter 

 numbers are unstarred, or (2) twenty-eight 

 chapters — numbers 1 through 4 and 19 

 through 42. 



A two-semester lecture course (meeting 

 a total of about 60 to 90 periods) can be 

 based upon (1) the first eighteen chapters 

 for the first semester and the last twenty-four 

 chapters for the second semester, or (2) all 

 thirty unstarred chapters for the first semes- 

 ter and all starred chapters and sections for 

 the second semester. 



Acknowledgments 



I wish to thank my wife, Reida Postrel 

 Herskowitz, for preparing the typescript, and 

 my sons, Ira and Joel, and my present and 

 former students for numerous suggestions. 



