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Genetic interactions involving major genes at the dwarf locus in egg-type chickens
Randolfo William Silvestre Custódio
Departamento de Genética, Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Caixa Postal 83, 13418-900 Piracicaba, SP, Brasil. R.W.S.C. is the recipient of a CNPq fellowship.
ABSTRACT
Three egg-type stocks segregating dwarf (dw) and bantam (dwB) genes in female progeny were produced from the same 18 heterozygous (dwB/dw) sires used to inseminate dams f three different genotypes: normal (dw+), dwarf (dw) and bantam (dwB) dams. The heritability f 8-week body weight estimated from full-sibs f the same phenotype f progeny was 0.40, and that estimated from paternal half-sibs f the same phenotype (dwarf or bantam), and from the same genotype f dam was 0.38. Therefore, maternal and non-additive effects within genotypic classes of dam made little contribution to the genetic variance for 8-week body weight among their progeny. The interaction f sires (S) with genotypes (dw+, dw and dwB) f dam (G) was significant at the 5% level. This indicates that the rankings f the sires within each one f the three genotypes f dam were not the same, probably due to non-additive genetic variation among genotypes f dams. The evidence indicated that in general the genes from individual sires combined differently with each type f dam (G). Those genes which combined well with the genes from normal (dw+) dams combined poorly with both the genes from the dwarf (dw) and the genes from the bantam (dwB) dams. The interaction f sires (S) with phenotypes (dwarf and bantam) f progeny (P) was significant at the 10% level. The results indicated a probable gene x genotype interaction for 8-week weight between genes at the dwarf locus (dw and dwB) and the background genotype (single and /or polygenes). The correlation among paternal half-sibs was influenced more by the S x G than by the S x P interaction, but the effects tended to be cumulative.
Keywords: major genes; dwarf locus; chickens.
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