[Chap. XXXVIII HYBRID SEGREGATION 465 



neither would the factors R and w. We may now represent all these facts 

 briefly, including also the union of the different eggs and sperms, and the 

 resultant genotypes of the progeny. 



Genotypes of 

 Parents 



Factors in 

 Gametes 



Genotype of All 

 Fi Hybrids 



Factors in 

 Gametes of 

 Hybrids 



TTRR 



TR 



ddww 



dw 



TdR^ 



TR, Tw, dR, dw 



(Factors in Sperms) 



TR, Tw, dR, dw 



(Factors in Eggs) 



TR 



(Selfing) 

 Tw i dR 



dw 



TR 

 Tw 

 dR 



dw 



Genotypes of 

 F2 generation 



Within the diagram are represented the genotypes of all the diflFerent 

 kinds of progeny with respect to height and flower color that may be 

 obtained from the hybrid pea having the genotvpe TdRw, and also the 

 ideal proportion in which they may be expected to occur in the field if 

 the total number of plants is very large. Note that many of the plants 

 that would appear to be similar in the field differ from each other 

 in their hereditary constitution. 



By using the same principles, one may determine the probable progeny 

 of crosses between other pure lines of peas, such as ( TTYY ) X ( ddgg ) 

 and (TTgg) X (ddYY). Mendel experimentallv proved that each of 

 the fourteen factors which he studied in peas segregated in the same 

 manner. 



Three characters considered simultaneously. No new problems arise 

 when three characters, such as Mendel studied in peas, are considered 

 simultaneously. Thus Fi hybrids of the pure lines that have the geno- 

 types TTRRgg and ddwwYY would all have the factors TdRwYg, and 

 considering these three characters alone there would be eight different 



