86 GENETICS IN RELATION TO AGRICULTURE 
the segregation is in the ratio 9 rough black :3 rough white :3 smooth 
black :1 smooth white. These relations are shown diagrammatically 
in Fig. 40. The factor relations are very simple. The genetic constitu- 
tion of the smooth black race is rrCC and of the rough white race RRcc, 
where R is a factor for rough coat and its allelomorph r a factor for 
smooth coat, and C and ¢ are factors for colored and albino coat respec- 
? pars SOK Mg ry 
; Ann 
A, ys LE BS 
Fie. 40.—Results of crossing smooth black and rough white guinea-pigs. F1 is rough 
black. F2 is in the ratio 9 rough black : 3 rough white :3 smooth black : 1 smooth white. 
(After Baur.) 
tively. The Fi RrCc is rough black because of the dominance of these 
two characters over their allelomorphs. When F, individuals are bred 
together the F, segregates in accordance with normal dihybrid expecta- 
tions as shown in the checkerboard in Fig. 41. 
This experiment shows how easily new races may be established, for 
in F2 two entirely new combinations of characters were obtained, namely, 
rough black and smooth white. Of the rough black individuals only 
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