CHAKACTEKISTICS OF PEDIGREES — HOMOZYGOSIS 



59 



sary to calculate his contribution to the homozygosis before cal- 

 culating that of Korndyke Butter Girl Johanna 2d. Following the 

 protocol we have the results shown below. 



INDIVIDUAL 



COMMON ANCESTORS OF 

 SIRE AND DAM 



fa 



n 

 1 



n' 

 1 



1 



2 



(l)n+n'+i (1 +/ ) 



Korndyke Butter 

 Boy 38496 



Manor DeKol 21226 







0.1250 



Korndyke Butter 

 Girl Johanna 2d 

 183646 



Korndyke Butter Boy 



38496 

 Johanna Aaggie 2d's 



Lad 26941 



0.125 

 



1 



2 



0.1406 

 0.0313 











0.1719 



The percentage of homozygosis is % (1 + 0.1719) X 100 =58.60 

 per cent. 



With these illustrations before us the complete significance of this 

 coefficient may be considered further. As indicated above the 

 coefficient gives the percentage increase of homozygosis or conversely 

 the percentage decrease in heterozygosis, when the animal pedigreed 

 has its unknown ancestors random mated. Thus the coefficient 

 really gives the percentage decrease in heterozygosis relative to the 

 stock to which the pedigrees are traced. If the percentage of 

 heterozygosis happens to be 50 per cent in the latter stock, J (1 

 + F ) X 100 gives the percentage of homozygosis in the animals 

 dealt with. In general, if p' is the percentage of heterozygosis in 

 this foundation stock, the percentage of heterozygosis in the animal 

 Oispo = v' (1 ~~ ^o) X 100. The assumption of previous random 

 mating for the fourth generation animals in any fourth generation 

 pedigree is undoubtedly not correct. While the actual percentage of 

 heterozygosis in any stock can hardly be estimated, it is probably 

 low when all the factors for the inherited characteristics of the 

 species, genus, order, and phylum are considered. Thus what is 

 really calculated, a point Wright is very careful to emphasize, is 

 the degree of change in the direction of homozygosis. The impor- 

 tance of the coefficient Fq is not to be minimized by these considera- 

 tions but rather strengthened. 



Calculate the amount of homozygosis for each of the pedigrees. 

 Tabulate the results for the whole class in the four groups, Ad- 



