GENETICS — STERN 267 



respiration and fermentation, in synthesis and decomposition. And 

 emerging from these phenomena, we are approaching from the aspect 

 of genie action differentiation and development, maturing, aging, and 

 death. 



As unbelievably remarkable as the functioning of an organism 

 is under the guidance of its genes, we have not yet spoken of the 

 still more remarkable fact that an organism can produce another 

 organism, that it can reproduce. Once, in the century of rationalism 

 and deism, some men believed that they could dispense with the solu- 

 tion of this biological enigma by laying it directly in the hands 

 of the Creator. They thought that a man's reproductive cells, his 

 sperm, were fully preformed little men, in turn containing inside 

 their tiny bodies still smaller fully preformed human beings to con- 

 stitute the grandchildren and so on in ever smaller proportion the 

 encapsuled miniatures of all future generations. In terms of molec- 

 ular biology this picture dissolves if it ever did have justification. 



Reproduction of an organism, basically, has become reproduction 

 of genes. Reproduction of a gene is an elementary process, the 

 copying of an original molecular configuration within a cell. How- 

 ever dependent this copying process is on the preexistence of the 

 larger, living assembly of parts which constitutes a cell, genie repro- 

 duction becomes accessible to study by the physicist and chemist. 



It is at the genie level, once more, that the problems of the evolution 

 of living forms at present find their most fundamental treatment. 

 If the genes of an animal or plant are responsible for its given 

 nature, how is it possible that this nature changes in the course of 

 biological history ? If evolution implies deviation from conservative, 

 accurate reproduction of an organism, the genetic interpretation 

 demands deviation from conservative, accurate copying of the gen- 

 erators of living form. Genetics indeed has demonstrated that the 

 so perfect copying process of the genie matter leaves room for some 

 imperfections; that the stabilizing transmission of exact replicas 

 of parental genes is accompanied by occasional upsetting lapses in 

 which a new kind of gene originates and causes the appearance of 

 hereditary newness. Some of these lapses are known to us in detail : 

 rare cases where the copy of a gene remains with the original gene 

 assembly instead of becoming part of the general duplicate; or rare 

 cases where genie material gets lost from the genie assembly. Other 

 lapses in exact copying may consist in a permanent change within 

 the molecular makeup of a gene itself, a change which may have 

 occurred before the gene began its reproduction, or may have been 

 an error in copying itself. 



The occurrence of such changes has been known for some time. 

 They initiate 'permanent newness, and their discovery is possible 



