426 Genetics of Sex Determination 



anism affect the control of all the different sexual attributes? Can the 

 balance mechanism be explained in a different way? Is it possible to 

 explain the facts without the idea of balance? Is the balance mech- 

 anism of sex determination widespread or restricted to special organ- 

 isms? What other t>pes of sex determination have been established? 

 These and other general questions will be the subject of our discussion. 



PRIMARY GENETIC 

 POSSIBILITIES 



If the phenomenon of genetically controlled intersexuality were not 

 known, the mechanism of the sex chromosomes could be given a very 

 simple, I might even say naive, if not even primitive, meaning. We 

 could assume that in the autosomes a number of determiners for all 

 individual female and male traits were represented, meaning, in ani- 

 mals, for ovaries and testes, for female and male external and internal 

 sex organs, for sexual differences in any part of the body (e.g., in 

 insects, color, segmentation, size and shape, behavior, and almost 

 every t\pe of structure). The X-chromosomes would not contain any 

 sex determiners but only something which simultaneously inhibits the 

 action of one set and enhances that of the other set of determiners. 

 This something, in terms of genes, would be realizator or trigger genes, 

 which in one dose can act in favor of only one group of the basic 

 autosomal sex genes; and in two doses, in favor of the other group. We 

 could express this differently by saying that in male heterogamety 

 (vice versa with female one) the male autosomal sex genes are more 

 frequent or more active than the female genes, and therefore two 

 doses of the trigger genes are needed in order to suppress this 

 superiority. It seems that such an idea is still entertained by Wester- 

 gaard (see 1948, 1953), mutatis mutandis, for the specific features of 



