A quantitation of the influence of the chick embryo genotype on tumor production by Rous sarcoma virus on the chorioallantoic membrane

Abstract

Tumors produced by Rous sarcoma virus inoculated by standard procedures onto the chorioallantoic membranes from 532 F 5 generation embryos from a cross between the Giant Jungle Fowl and White Cornish strains of chickens were counted. These embryos were from 13 sires and 59 dams. An analysis of variance of the tumor counts was made relative to the variation in tumor counts on chorioallantoic membranes between embryos from the same dam mated to the same sire. This analysis revealed a significant difference between dam progenies within sires within dilutions ( P > 0.01) and a significant difference ( P > 0.01) between sires within dilutions. Estimates of heritability of the number of tumors per membrane were 0.28 and 0.78, using the sire and dam components of variance, respectively. These results imply that about 28% of the total variation in numbers of tumors is due to additive gene action. Moreover, there are important extrachromosomal influences transmitted by the dams. This is evident from the much larger estimate of heritability obtained from the variance component for dams.