354 CELL HEREDITY 



concepts, and new experimental approaches to the understanding of 

 genetic control mechanisms in ci'll integration. We ha\e seen that these 

 investigations range from the analvsis of the replication of nucleic acids 

 and the s\nthesis of proteins in defined in vitro systems to the transfer 

 of whole nuclei from cell to cell. All the combined knowledge of 

 biological and plusical sciences is being drawn upon to devise experi- 

 ments w hich w ill re\eal the dvnamic interactions among cell parts. 



In this effort, it is now beginning to appear that the regulatorx role 

 of genetic material is of central importance. The abilitv to stuck the 

 genetic control of repression and regulation of enzvme formation in w ild- 

 type cells as well as in mutants has pro\ ided both experimental ap- 

 proaches and concepts which w ill undoubtedly be of wide applicability 

 in all organisms. The concept of rate-controlling genes is a \er\- old 

 one in genetics, first studied and discussed extensixely bv Goldschmidt 

 in the 1920 s. It is much more available to analysis in its present form, 

 in w hich it can be pursued at the specific level of enz\me synthesis. 



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 Cohen, G. N., and J. Monod, 1957. Bacterial permeases. Bact. Rev., 21:169- 



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