GENES AND CHARACTERS 



317 



single pair of determiners. In one experiment, according to 

 Babcock and Clausen, seven families with a total of 440 plants 

 produced white seeds on only one plant. 



Omitting further details, it has been found that color in this 

 case was determined by three different factors. The genotypic 

 formula for the parents may be indicated as AABBCC and aabbcc, 



Q (/-^Cp Cd cD 



T Y I __ Y 



CD- 



Cd- 



cD- 



cd- 



CD. CD 



Cd-CD 



1:0 



cD.CD 



1:0 



cd 'CD 



15:1 



CD-Cd 



1:0 



Cd-Cd 



1:0 



cD-Cd 



15:1 



cd- Cd 



CD'CD 



1:0 



Cd-cD 



15:1 



cDcD 



1:0 



cd-cD 



3:1 



f 



CD. cd 



15:1 



Cd'cd 



3:1 



3:1 



cd ■ cd 



0:1 



Fig. 182. — Punnett square with diagrammatic figures to illustrate the inheri- 

 tance of seed capsule shape in Bursa (B. bursa-pasloris x B. heegeri). The 

 two duplicate factors are represented l)y oblique ruling in opposite direc- 

 tions, and the number of factors present by the spacing of the lines. The 

 ratios indicate the expectation in the F3 generation from self-fertilized 

 individuals. (After ShuU from Babcock and Clausen's Genetics in Relation 

 to Agriculture by permission McGraw-Hill Book Company, Inc.) 



and that of the Fi generation as AaBbCc. In the F2 generation 

 the recombination of these factors occurs in sixty-four waj'S 

 according to the law of trihybrids, but only one out of the sixty-four 

 has the homozygous recessive organization which produces white 

 grains. All heterozygous individuals, such as AABbCc, AaBbcc, 

 aaBbcc, etc., produce red grains, varying in depth of color according 

 to the number of dominant factors present. Out of these red 



