THE M U TA TED GENE 115 



3. The most frequently found cases show complete dominance 

 of the highest member of the series over all others and inter- 

 mediate behavior of all compounds not involving the highest 

 member. To this group belong many of the best known series 

 in animals and plants, e.g., the white-eye series of Drosophila 

 (wild, coral, blood, cherry, apricot, eosin, ivory, tinged, buff, 

 ecru, white). 



4. The theoretically most important is the case in which the 

 situation is as in the last-mentioned group, but in addition the 

 highest member is not dominant over the lowest ones. To this 

 important group belong also the cases in which the lowest mem- 

 bers are more or less lethal in homozygous condition. Examples 

 of this type will be discussed in detail later. 



5. Special cases requiring independent consideration, e.g., 

 the pattern of silkworm larvae: P s striated, p m dark brown, 

 P normal, p unpigmented. From p m to p the darker alleles are 

 dominant over the lighter ones. P is dominant over the two 

 lower alleles but only incompletely so over the highest p m . But 

 of course here no strict sedation is involved, as striped is a new 

 character in the series. 



There is a second set of facts which become visible when 

 different effects of the same series upon different traits are 

 involved (pleiotropy). Here the following possibilities are 

 realized: 



1. The different effects may be arranged in parallel series, and 

 within these series dominance is also parallel, e.g., the albino 

 series of rabbits and mice affects in a parallel seriation black 

 pigmentation, yellow pigmentation, and eye color; and in 

 each the highest member is dominant, and the other com- 

 pounds intermediate. But (as a threshold effect, see page 85) 

 this does not mean that the highest member is always only the 

 first one. 



2. Within each series of pleiotropic effects, dominance behaves 

 in an orderly way; but the series are not parallel in the different 

 traits affected; e.g., the aleuron-color and pericarp-color series in 

 maize (R and P) affect the color of aleuron, vegetative parts, 

 anthers, and pericarp. Everywhere deeper color is dominant 

 over more dilute. But if the series of alleles is arranged for 

 aleuron from dark to light, the effect upon the three other 

 characters is not parallel; they have each their own sedations. 



