DIRECTED HEREDITARY CHANGES OF 



FERMENTATIVE PROPERTIES OF YEAST BY 



A SPECIFIC SUBSTRATE 



K. V. KossiKOV 



Institute of Genetics, Academy of Sciences of the U.S.S.R., Moscow 



Investigations into the directed changes of micro-organ- 

 isms are in full swing in the Soviet Union. At the end of 1951, 

 a conference devoted to this problem was organized under the 

 auspices of the Institute of Microbiology of the Academy of 

 Sciences of the U.S.S.R., the transactions of which were pub- 

 lished in 1952. Monographs on the variability of micro- 

 organisms were published by Kalina (1952) and Muromzev 

 (1953). Investigations are under way on the adaptation of 

 micro-organisms to various toxic substances (Imshenetsky, 

 1953; Planelies and Moroz, 1956; and others). 



The extensive experimental data obtained in recent years 

 have shown more clearly the inconsistency of the mutation 

 selection theory in explaining the phenomena of adaptation 

 of micro-organisms to various bactericidal substances and to 

 new sources of nutrition. The nature and speed of the 

 adaptational changes occurring in these organisms, the 

 quantitative and qualitative dependence of these changes on 

 the dose and length of action of the substance to which the 

 organism became adapted, and also a number of other factors 

 observed in the study of these phenomena cannot be accounted 

 for by mere selection of spontaneous mutations. 



Dean and Hinshelwood (1953), discussing the main issues 

 of the theory of spontaneous mutations, and of the selection 

 that follows them, came to the conclusion that in some cases, 

 at any rate, changes may occur in populations — according to 

 this theory — which do not take place in reality. 



The need to explain these phenomena, starting from other 



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