GENETICS — STERN 265 



What are these elements? Mendel himself gave them symbolic 

 letters, A and B and C, representing the characteristic traits which 

 he was studying. There is no doubt that he did not think of A as 

 being redness of flowers but rather as an agent transmitted through 

 the parental germ cells, whose action, after growth and development 

 of the fertilized egg cell into a mature plant, resulted in the presence 

 of red pigment in its flowers. His early followers expressed this con- 

 cept in the word "factor" (i. e., maker), the factor A leading to the 

 production of redness. The famous term "gene" at first had no other 

 connotation. It was to express the fact that the traits of the or- 

 ganism are generated by "separable, and thus so-to-say independent 

 'states,' 'factors,' 'units,' or 'elements' in the make-up of the germ 

 cells. . . ." 



The term "gene," however, did not permit itself to be confined in 

 the lofty heights of hypothesis-free abstraction. When the gene was 

 recognized as being associated with the chromosomes, an interpreta- 

 tion of its nature in terms of matter became an obvious need. We are 

 still in the middle of this process of interpretation which takes place 

 at the molecular level. Where the speculations of former times 

 thought of elementary submicroscopic living units, themselves en- 

 dowed with the mysterious properties which constitute life, we now 

 regard the life of cells and of whole organisms as the resultant of 

 chemical and physical processes which involve properties and re- 

 actions of molecular matter of the same kind which the chemist and 

 physicist study in test tubes and with the spectroscope. It is a truism 

 that this is not all. The mystery of life remains, but it is now seen 

 in the integrated coupling of the molecular phenomena and the con- 

 sequences of this over-all molecular organization, not in the elementary 

 processes themselves. 



Thus our problem has doubled. Wliile we want to know, justifi- 

 ably, the gene's molecular structure, our task would not be completed 

 with the attainment of this knowledge. If we could write down 

 today an accurate structural formula of a gene molecule, the prob- 

 lems of genetics would not yet be solved. Indeed, we could imagine 

 that the cellular chemist might have provided us with this structural 

 knowledge before the science of genetics had been born. The mo- 

 lecular recognition would not have given us the gene, the generator 

 of the organism's traits, but a molecule. The biological problems of 

 genetics depend on molecular processes, but are larger than they. 



As it is, the physicochemical analysis of the chromosomes has not 

 yet led to the gene. Beautifully refined micromethods made us recog- 

 nize various proteins and nucleic acids, and even gave us specific ar- 

 rangements of regions relatively rich or poor in these substances. It 

 will be a long road, however, toward the recognition of the specificity 



