186 ANTHOCYANINS AND GENETICS 



AB : 3Ab : 3aB : ab 

 AB : 7Ab : 7aB : ab . 

 AB : 15Ab : 15aB : ab 



'Coupling' was the term first employed for the phenomenon observed 

 among the offspring for the heterozygote AB.ab, 'repulsion' for the 

 phenomenon from the heterozygote Ab.aB. The terms are now rejected 

 in favour of the expression 'reduplication.' 



From evidence first obtained, it was thought that the repulsion 

 was complete, but later evidence is strongly in favour of partial 

 repulsion such as is expressed above. 



The relation between the gametic and zygotic series for a few terms 

 is explained in the following table: 



Partial coupling from zygote of form AB x ab 



Only those cases connected with anthocyanin pigmentation are 

 quoted in this account. As it happens, the first example noticed of 

 these phenomena was in the Sweet Pea (Lathyms) from F x plants 

 heterozygous for blue and red colour, and for long and round pollen. 

 The blues were, for the most part, long-pollened, and the reds, for the 

 most part, round-pollened. The partial coupling was shown to be: 



7BL : 1B1 : IbL : 7bl 



where B is blue colour, and L is long pollen. 



The second example was that of F a plants heterozygous for dark 

 and light axils, i.e. pigmented (anthocyanin) and unpigmented axils, 

 and fertile and sterile anthers. The coupling was shown to be 



15DF : IDf : IdF : 16df 



where D is dark axil, and F is fertile anthers. 



The first example of repulsion was noted in the F 2 from a plant 

 heterozygous for blue and red flowers, and for erect and hooded 



