152 



GENETICS 



two complementary genes that follow the behavior of a 

 dihybrid. (See Chap. V, par. 10.) 



The gametic formulae for the two strains of white 

 sweet peas used in this experiment are Cp and cP, 







CP 







cP 



ep 



11 



12 



16 



A$ 



J 





FIG. 33. Diagram to illustrate the possible progeny from two 

 heterozygous purple sweet peas according to data from 

 Bateson. C, color gene (large circles) ; c, absence of C 

 (small circles) ; P, pigment gene (large crosses) ; p, absence 

 of P (small crosses). In the zygotes within the checkerboard 

 squares the gametic symbols are superimposed. 



respectively. C stands for a color gene without which 

 no color can appear, and c is the absence of this fac- 

 tor, while P represents a purple pigment gene which 

 finds expression in the somatoplasm only when taken 

 together with the color gene C. The small letter p 



