THE MUTATED GENE 99 



A special type of genie action controlling definite chemical 

 processes is, finally, the production of the stuffs that are respon- 

 sible for serological specifities. The bodies that make for the 

 blood-group differences belong here. A recent study by Abder- 

 halden (1936) has revealed another group. Rabbits injected 

 with proteins from other animals produce proteinases which 

 specifically split those proteins and which may be isolated from 

 the rabbits' serum. By aid of the specificity of these enzymes 

 Abderhalden demonstrated protein differences between different 

 linos of guinea pigs, distinguished by single genes. If this should 

 be confirmed, it might load to interesting conclusions. 



6. THE GENE IN HETEROZYGOUS STATE 



Since early Mendelian days, it has generally been assumed that 

 the phenomenon of dominance must one day lead to an insight 

 into the nature of the gene. Correspondingly, it was assumed 

 that dominance or recessiveness were attributes of individual 

 genes. Bateson, as is known, believed that dominance is the 

 presence and recessiveness the absence of the thing called a gene, 

 an idea that, however, was refuted at the outset by Correns' 

 (1899) discovery of dominance of two recessive genes over one 

 dominant in the triploid endosperm of maize. Later dominance 

 was attributed to different potencies of the genes (Davenport, 

 1908; Kellogg, 1908), which might change even individually. 

 ( )nly slowly geneticists began to realize that dominance is not a 

 v" property of the gene but of the phenotype. It seems that 

 Tower (1910) was the first to report that dominance could be 

 changed at will in the same heterozygote of Leptinotarsa undecim- 

 lineata signaticollis by proper control of temperature and 

 moisture. At about this time, some geneticists realized that domi- 

 nance was not a property of the gene but something "floating, 

 capable of being shifted," as Goldschmidt expressed it in the 

 first edition of his textbook (1911a). 



As far as I know, the first trial to express dominance in terms 

 of development was made by Goldschmidt (1916c, 1917c), 

 when he found that a case of so-called change of dominance dur- 

 ing development had to be explained by the respective velocities 

 of processes of progressing pigmentation. Dominance then was 

 controlled by certain time relations of processes or reactions 

 occurring during development which could be expressed in a 



