MS 



l'llYSloijHiKAL GENETICS 



is thai the genes in question exercise a highly .specific action upon 



such synthetic chemical processes as oxidation, met hylation, 

 addition of SUgar or acid residues at definite locations, and con- 

 trol of pll. in addition to the production of a more generalized 

 basic substance. Another point may be derived from the fact 

 that in many of the cases the Wild-type color is the most highly 

 oxidized one; mutant genes then prevent complete oxidation, 

 which again may work by controlling the rates of a decisive proc- 

 ess which might have to do with the specific catalyst involved in 

 the reaction. But, as Haldane (1935) remarks, it is very difficult 

 to draw definite conclusions upon the action of a gene from such 

 facts. "The gene which is responsible for the methylation of a 

 certain hydroxyl may be itself a diastase, may produce one, or 

 may be concerned with a reaction which liberates the necessary 

 energy for the action of an already present diastase." But, in 

 a general way, Haldane, like many others, assumes that the 

 action of the gene results, in most cases like those which were 

 mentioned, in the production of a specific catalyst. 



Table 11 



(After Scott- Moncrieff) 



Examples of gene action 



Varieties 



Dominant Recessive Gene 



I. Yellow plastids: 



< 'keiranthua cheiri 



II. Yellow anthoxanthin : 

 Antirrhinum majus 



III. Ivory anthoxanthin copigment: 



1'ri inula sinensis 



IV. General anthocyanin: 



Dahlia variabilis 



V. Specific anthocyanin: 



Pa-paver Rhoeas 



VI. Oxidation of anthocyanin aglycone 

 Antirrhinum majus (3-rhamnogluko- 



sides) 



VII. Oxidation and met hylat ion of antho- 

 cyanin 



Pelargonium zonale (3—5 dimonosides) . . 



VIII. Local change in pH: 



Primula sinensis 



Magenta 



Malvidin 

 Pink 



Magenta 



Red 



I'durijonidin 

 Salmon 



Blue 



X 

 R 



