352 Action of the Genetic Material 



upon this conclusion could be made by a measuring of +^/0, first 

 with being the small deficiency used in the experiments, and then 

 with based upon haplo-IV, which has no position effect, though it 

 might do some shifting via genie balance change.) 



While the basic data do not require any other explanation than 

 one resting upon dosage, or a potency of certain alleles acting in the 

 same sense as dosage, another set of data was presented by Stern in 

 regard to triplex conditions which looks as if in certain combinations 

 ci had not the cumulative dosage effect but an antagonistic effect. 

 The following are the facts ( > meaning more normal, being the 

 small deficiency, M-4): 



1. ci +2 > ci ci +2 



2. ci +2 > ci ci +2 



3. +2 > ci ci +^ 



Thus the presence of two ci with one plus reverses, in all comparisons 

 with the diploid condition, the additive dosage action of ci: this 

 combination is always more abnormal, while such triplex ones as ci 

 ci ci and ci ci follow the dosage rule. We might express the result 

 also by saying that two ci are dominant over +, while the usual 

 behavior is the opposite. Clearly, some new element has entered the 

 group of facts. Stern expresses this by saying that ci has a positive 

 vein-producing capacity as well as a negative one. In the presence of 

 only ci loci, the positive is greater than the negative; in the presence 

 of a + allele the opposite is the case. This, of course, is only an 

 abstract description of the facts. To make it concrete, Stem assumes 

 (as I mentioned when discussing position effect) that each allele has 

 two properties: a combining power (with the substrate) and an 

 efficiency factor. Now +^ and ci have different combining powers, 

 using different amounts of substrate. Regarding the efficiency factor, 

 it is assumed that +^ and ci interact with the substrate to form an 

 identical product P (see above) or two different ones of identical 

 effectiveness. The efficiencies e +^ and e ci mean, in this case, the 

 relative amount of P +^ and P ci formed by the allele per unit of 

 substrate used. If now the efficiency of ci is lower than that of +^, 

 and if the amount of substrate is limited to an amount below that 

 which ci and + together can utilize, the competition for the substrate 

 between the two kinds of alleles of the heterozygote -f^/ci/ci will 

 result in the +^ genes not obtaining enough substrate to produce its 

 maximum effect, while the ci genes will use their fraction of substrate 

 less efficiently than -f^. Hence the limited amount of substrate present 



