Extranuclear Genes and Nuclear Genes 



419 



SUMMARY AND CONCLUSIONS 



The cytoplasm can contain extranuclear genes which are not known to be episomes. In 

 some cases the extranuclear genes seem to be foreign organisms (sigma probably, kappa), 

 in other cases they appear to be normal constituents of the cell (chloroplasts, mating type). 

 Nuclear and extranuclear genes show the following interrelations: the former can mutate 

 the latter; both may interact in the production of a particular phenotype, sometimes operat- 

 ing as a feed-back system. 



REFERENCES 



Beale, G. H., The Genetics of Paramecium Aurelia, Cambridge, Cambridge University Press, 

 178 pp., 1954. 



Campbell, A., "Conditions for the Existence of Bacteriophage," Evolution, 15:153-165, 1961, 



Rhoades, M. M., "Plastid Mutations," Cold Spr. Harb. Sympos. Quant. Biol., 11:202-207, 

 1946. 



Rhoades, M. M., "Interaction of Genie and Non-Genie Hereditary Units and the Physiology 

 of Non-Genie Inheritance," in Encyclopedia of Plant Physiology, Ruhland, W. (Ed.), 

 Vol. 1, pp. 19-57, Berlin, Springer Verlag, 1955. 



Sonneborn, T. M., "The Role of the Genes in Cytoplasmic Inheritance," Chap. 14, pp. 291- 

 314, in Genetics in the 20th Century, Dunn, L. C. (Ed.), 1951. 



Sonneborn, T. M., "Kappa and Related Particles in Paramecium," Adv. Virus Res., 6:229- 

 356, 1959. 



Sonneborn, T. M., "The Gene and 

 Cell Differentiation," Proc. Nat. 

 Acad. Sci., U.S., 46:149-165, 

 1960. 



Hl^il 



Tracy M. Sonneborn, about 1960. 



