EVIDENCE FOR A GENETIC-VARIATION IN THE MITOCHONDRIAL GENOME AFFECTING TRAITS IN WHITE LEGHORN CHICKENS

A mitochondrial Mspl RFLP which was coselected with Marek's disease (M D) resistance in White Leghorn chickens was mapped to the NADH subunit IV. The RFLP was due to a transition, resulting in the change of the low-usage threonine triplet ACT (Mspl(-) allele) to the high usage tri plet ACC (Mspl(-) allele), Trait association studies within an unselec ted strain revealed that the Mspl(-) allele whose frequency was reduce d in MD resistant strains was associated with high body weight and hig h egg specific gravity (a measure of eggshell thickness). Analysis at three different time points indicated a significant interaction betwee n the mitochondrial genotype and the growth hormone genotype in early but not in late adulthood. The analysis indicates that mitochondrial v ariants may contribute to phenotypic variation in chickens and that su ch contributions may be dependent on the genetic background.