tailieunhanh - báo cáo khoa học: "Heritability of a canalized trait: teat number in Iberian Teresa pigs"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Heritability of a canalized trait: teat number in Iberian Teresa pigs | Génét. Sél. Evol. 1986 18 2 173-184 Heritability of a canalized trait teat number in Iberian pigs . TORO Maria Teresa DOBAO J. RODRIGANEZ and L. SILIO Departamento de Genética Cuantitativa y Mejora Animal Institute Nacional delnvestigacionesAgrarias Carretera de La Coruna Km. 7. 28040 Madrid Espagne Summary Teat number is a discontinuous and often canalized trait in populations of domestic swine. This is the case in the Iberian pig where 90 p. 100 of individuals show 10 teats. The estimation of genetic parameters for this discrete and strongly leptokurtic trait presents difficulties similar to those encountered in dichotomous ones and several specific methods of estimation have been suggested generally assuming the existence of an underlying normally distributed random variable. Heritability estimates of teat number based on 30 271 animals of three strains of Iberian pig have been obtained both using conventional correlation and regression methods and through 3 specific techniques proposed by Robertson Gianola and Tallis These methods allow one to estimate what proportion of the heritability of the assumed underlying variable h2 can be accounted for by the heritability estimated in the observed scale ho . The estimated proportion ranged between and depending on the degree of canalization of the trait in the 3 different populations considered. The use of these specific methods despite their interest may present serious difficulties in practical breeding conditions. Key words Heritability discrete traits teat number canalization Iberian pig. Resume Héritabilité d un caractère canalisé le nombre de tétines chez le pore Ibérique Le nombre de tétines est un caractère discret qui est souvent canalise dans les populations de pores domestiques. Tel est le cas chez le pore Ibérique où près de 90 p. 100 des individus possedent 10 tétines. L estimation de paramètres génétiques pour ce caractère discret et à une forte lepto-kurtosis pose des problèmes similaires a