WRIGHT 79 



the lack of adequate tools and research methods to permit such 

 studies. There was little questio?i that the gene played an important 

 part in growth and development, but as little ijiformatio?! as to how 

 it did it. 



Wright takes advantage of the findings of biochemistry and his- 

 tology in the development of his hypothesis concerjiing the produc- 

 tio7i of coat color in animals. He investigates the actual mechanism 

 of color formatio?!, and ijidicates the mode of actio?j of the gene i?i 

 this process. This paper lays the foujidatioji for the field of biochem- 

 ical or physiological ge?ietics, and in fact still remains as the basic 

 source of informatio?i ajid the startifjg point of ?noder?2 investigatio?i. 

 Wright conti?Jued his thoughtfid investigations i?i this field for many 

 years, and in 1941, he wrote a paper called ""The Physiology of the 

 Ge?2e," published i?i Physiological Reviews, vol. 21, pp. 487 -S 27. 

 This paper is too long to reproduce here, but I recommend it most 

 strongly to the reader. 



One of the most sigfiifica?it events m the history of twe?itieth 

 century genetics, in my opinion, is the shift in emphasis exemplified 

 by this paper. The focus of attention on the ways the gene goes 

 about doing what it does, rather tha?j on the ?nechanics of its tra?is- 

 missio7i plus its idejitification through its terminal expression, has 

 given ge?ietics a central positio?i iji the u?ider standing and inter- 

 pretation of biological phenomena. A thorough knowledge of the 

 various modes of action of the gene will re-emphasize the imitary 

 nature of the field of biology. The more we learn about the ge?7e^s 

 mode of action the more obvious it becomes that the phe?iomena of 

 embryology, biochemistry , physiology, evolutio?i, ajid systematics— 

 in fact, all major fields of biology— are for the most part only facets 

 of this one coinmon problem, a?id solutiofi of one aspect of gene 

 actio?! is likely to have repercussions in several other diverse areas. 



Heredity as looked upon since the than it did half a century ago, the 

 time of Weismann is relatively simple problem of development has become 

 to understand. It consists merely in the more complex. We see clearly that de- 

 persistence of a certain cell constitu- velopment is no mere unfolding and 

 tion (in the germ cells) through an growth of elements already present in 

 unending succession of cell divisions, the fertilized t^^ or even a sorting out 

 We see something of the mechanism, of germinal rudiments for parts of the 

 back of this persistence, in mitosis. We organism. The germ cell has a certain 

 understand complications brought highly complex constitution, the adult 

 about by the reduction division and organism another such constitution,' 

 bv^ the union of two germ cells at and between the two is no simple one-, 

 fertilization. Thus we no longer puz- to-one relationship. An almost infi- , 

 zle over the problem as to how an nitelv complex series of interactions 

 individual packs his characters into of elements must take place at each 

 his reproductive cells, the problem stage of development. The difficulty 

 which led to Darwin's theory of pan- in the study of heredity is that the 

 genesis. But if heredity seems simpler characters of the germ cell must be 



