46 



BULLETIN 1121, U. S. DEPARTMEN l' OE AGRICULTURE. 



Table 13. — The vigor of heterozygosis to he expected iii various experiments v.ith respect to 

 characters determined in various degrees by the sire, dam, and the animal in question. 



Character deter- 

 mined by- 



Vigor of iieterozygosis, 1 in random-bred stock, in ultimate inbred stock. 



Sire. 



Dam. 



Young. 



B. 



Al. 



A2. 



A3. 



A4. 



A5. 



Aoo. 



CO. 





 

 

 

 

 i 

 1 





 i 



1 

 i 

 



1 



f 



6 





 



1 



0.750 



.812 



.875 



.938 



1.000 



1.000 



1.000 



0.625 

 .656 

 .687 

 .719 

 .750 

 .750 

 .750 



0.500 

 .531 

 .562 

 .594 

 .625 

 .625 

 .625 



0.406 

 .430 

 .453 

 .476 

 .500 

 .500 

 .500 



0. 328 

 ..347 

 .367 

 .386 

 .406 

 .406 

 .406 





 

 

 

 

 

 



l.OOO 



.750 



.500 



.2.50 















Character deter- 

 mined by- 



Vigor of heterozygosis, 1 



n random-bred stock, in 



ultimate inbred stock. 



Sire. 



Dam. 



Young. 



CI. 



C2. 



C3. 



C4. 



C5. 



Coo. 



CA. 



AC. 



cc. 











1 



0.500 



0.500 



0.375 



0.312 



O250 







1.000 



1.000 



l.OOO 







i 



1 



.625 



.500 



.406 



.328 



.261 







.750 



1.000 



1.000 









h 



.750 



.500 



.438 



.344 



.281 







.500 



1.000 



l.OOO 







a 



i 



.875 



.500 



.469 



.3.54 



.296 







.250 



1.000 



1.000 







1 







1.000 1 .500 



.500 



.375 



.312 











1.000 



1.000 



§ 



h 







1.000 .500 i .500 



.375 



.312 







.500 



..500 



l.OOO 



1 











1.000 .500 1 ..500 



i 



.375 



.312 







1.000 







1.000 



Note that Experiments CC with the full vigor of the original stock 

 and C2 with half this vigor are constant in position regardless of the 

 relative importance of sire, dam, or the young themselves. 



These theoretical conclusions are based solely on the hypothesis 

 that the hereditary element in the various characters is determined 

 wholly by Mendelian factors and that there is more tendency for the 

 detrimental factors to be recessive than dominant. Comparison 

 with the actual results (Fig. 27) shows that the agreement is as close 

 as could be reasonably expected. 



Adult weight and resistance to tuberculosis are examples of char- 

 acters determined wholly by the young themselves. The percentage 

 raised of the young born alive seems to be determined about three- 

 fourths by the heredity of the young and one-fourth by the dam. In 

 total percentage raised, rate of gain between birth and weaning, and 

 weight at weaning, the breeding of the dam and of the young are 

 about equally important. The data for birth weight indicate that 

 here the breeding of the dam counts for about three-fourths, young 

 only one-fourth or less. The percentage born alive depends almost 

 completely on the dam. In frequency of litter, the heredity of young 

 counts for nothing, but the sire seems to have twice as much mfluence 

 as the dam. In size of litter there is complete determination by the 

 dam. The young per year and young raised per year are merely 

 combinations of certain of the other characters. For the last named 

 there is something like one-eighth determination by the young. 



One result which seemed rather puzzling was the relatively low 

 record of Experiment CG, in which the parents were selected as ex- 



