GENE RECOMBINATION AND HETEROSIS 



299 



as Brbr. Using these symbols, the genotype of the Fi is VvBrbr. The Vv gene 

 pair is carried on chromosome 1 and the Brbr gene pair on chromosome 7. 



Table 19.1 gives the comparative effect upon four quantitative characters 

 of genes associated in inheritance with Vv and vv and VV and vv, as deter- 



TABLE 19.1 



COMPARATIVE EFFECT UPON FOUR QUANTITATIVE CHARACTERS OF 



GENES ASSOCIATED IN INHERITANCE WITH Vv AND vv, AND 



VV AND vv; F-, GENOT\TES OF A BARLEY HYBRID 



* Weight of seed per plant is expressed in grams, spikes per plant in number, height of plant in inches, and 

 length of awn in millimeters. 



TABLE 19.2 



COMPAR.VTIVE EFFECT UPON FOUR QUANTITATIVE CHARACTERS OF 



GENES ASSOCIATED IN INHERITANCE WITH Vv AND VV, AND 



VV AND vv; F. GENOT\TES OF A BARLEY HYBRID 



* Weight of seed per plant is expressed in grams, spikes per plant in number, height of plant in inches, and 

 length of awn in millimeters. 



mined by differences between means of F2 plants. In every case, the differ- 

 ences between Vv and vv are greater than the differences between VV and vv 

 for spikes per plant, height of plant, and length of awn. With the exception 

 of the comparison between VV and vv within the brbr genotype, the differ- 

 ences are in favor of the two-row (Vv and VV) segregates as compared with 

 the six-row (vv) segregates. Within the brbr genotype, iJt) plants exceed the VV 

 plants for all three characters. As regards weight of seed per plant in every 

 case the six-row plants outyielded the two-row plants whether heterozygous 

 deficiens or homozygous deficiens. However, the differences between vv and 

 Vv were less than those between vv and VV. 



The data of Table 19.2 show that for all characters the Vv plants give an 



