Chapter 27 

 EXAMPLES OF APPARENT CYTOPLASMIC INHERITANCE 



The development of American genetics was most rapid during 

 the first World War. The American School concentrated on the con- 

 struction of chromosome maps and the precise repeatable type of 

 experimentation which developed with mapping techniques. There 

 was an effective separation from the German workers during the 

 war and the latter, led by Correns, concentrated on the exceptions 

 to Mendelism. This led to two different attitudes toward genetics 

 with the emphasis on exceptions to Mendelism by German workers 

 and a tendency to ignore such exceptions by Americans. Recently 

 in America there has been a recognition of the phenomena described 

 by the German workers and much discussion of cytoplasmic inheri- 

 tance especially by Sonneborn, and it is noteworthy that his early 

 training did not involve genetic indoctrination as a member or close 

 associate of the Morgan School. 



In yeast genetics we encoimtered many examples of non-Men- 

 delian phenomena and in our early work I interpreted these as in- 

 volving the hereditary transmission of autonomous cytoplasmic en- 

 tities. This was a rather difficult thing for me to do because I had 

 been thoroughly indoctrinated in Gene Theory by my long associa- 

 tion with Dr. Morgan and the other members of his famous staff. It 

 has been even more difficult to make the reorientation required to 

 interpret these phenomena in terms of the obviously faulty Winkler 

 Konversion hj^pothesis but tetrad analyses of heterozygous yeasts 

 give this view a new validity, because in this case it is possible to 

 differentiate Konversion from crossing -over. These facts and oth- 

 ers have led to the conclusion that most "cytoplasmic" inheritance 

 except that involving chloroplasts, rickettsias and other obvious 

 symbionts or parasites can be explained without assuming the exist- 

 ence of autonomous entities in the cytoplasm. The theory will be 

 presented in the Chapter 28. 



SELF -DUPLICATION 



Genes are often described as self-duplicating as if this character- 

 istic distinguished them from other cellular structures. However 

 self-duplication is a general characteristic of many cellular struc- 

 tures such as the plasma membrane, the chondriosomes, and the 

 achromatic apparatus. The entire cell is a self-duplicating structure, 



27-1 



