Componentes principales como fenotipos de sistemas biológicos complejos: Relación músculo-hueso en el ratón (Mus musculus)

principal components analysis classifies the phenotypic variation of a population into independent systems of correlated traits. it has been postulated that principal components can be used to identify genetic networks involved in regulating complex biological systems as each individual in the population has values which may be associated with phenotypes susceptible to be analyzed genetically. the technique was applied to fi ve traits involved in muscle-bone relationship (pesmus: gastrocnemius muscle weight; pestib and pesfem: weight of tibia and femur, and lonfem and lontib: length of femur and tibia) measured at 150 days of age in males (n = 336) and females (n = 319) of a segregating population (f2) of mice derived from crossing two lines selected for body conformation. the three first principal components explained almost the same proportion of the total variance (87%) in males and females. the first component (pc1) explained 60% of the generalized variance and was negatively associated with the fi ve muscle-bone indicators, so it may be considered as an indicator of body size. the second component (pc2) explained 15% of the total variance and was associated with bone length with little effect on bone weight and muscle weight so it can be interpreted as an indicator of skeleton length. the third component explained 12% of the variance and was associated with muscle weight, with little effect on bone weight and no effect on bone length, so it can be interpreted as an indicator of the biomass sustained. the results indicate the coexistence of independent sources of phenotypic variance in the characterization of this complex biological system that allow to identify particular combinations of the triad -body size, skeleton as a scaffold for soft tissues and biomass sustained.