682 



HEREDITY AND CELL DIVISION 



of contrasting characters, and he found, in all the combinations 

 which he tried, that the pairs were inherited independently. 

 The Fj generation showed only the dominant characters, but on 

 self-pollination an F2 was produced which contained all the 

 possible combinations of characters in the approximate propor- 

 tions given by multiplying together the F^ ratio for the different 

 pairs of characters. For a cross between plants from round and 

 yellow seeds (dominant) and plants from wrinkled and green 

 seeds (recessive) the Fg consisted of 



315 



lOI 



108 

 32 



round yellow seeds 

 wrinkled yellow seeds 

 round green seeds 

 wrinkled green seeds 



Further breeding showed that of these only the wrinkled green 

 seeds, thirty-eight of the round yellow seeds, and about the same 

 numbers of the new combinations wrinkled yellow and round 

 green, bred true ; the others were heterozygous for one or both 

 characters. If we represent the plants homozygous for roundness 

 by RR, for yellowness by YY, the corresponding recessives by 

 the lower-case letters, and the heterozygotes by Rr and Yy, 

 the numbers of the Fg come out as shown in Table X, column i, 



TABLE X. / 



which excludes a few which did not live. Column 3 shows the 

 fractions obtained by multiplying together the separate ratios 

 (i RR + i Rr + J rr) and (i YY + i Yy + i yy) already 

 known for the single pairs, and column 4 these fractions of the 

 total, to the nearest whole number. It will be seen that the 

 agreement is close. 



