[Analysis of phenotypic correlations between qualitative traits. I. Genetic analysis of the structure of relations...

The methods are presented by which the coefficients of phenotypical correlations between multifactorial characters and coefficients of criss-cross correlations for qualitative characters between relatives can be estimated. These coefficients can be calculated from the known incidences of the traits X and Y (qgx and qgy) in general population, the incidence of Y among X bearing persons, the opposite incidence of X among Y bearing persons, the incidence of Y among the relatives of X bearing probands and the incidence of X among the relatives of Y bearing probands. All these correlations can be used to estimate the genetic correlation between qualitative traits and thereby for the genetic analysis of the structure of phenotypical correlations between multifactorial diseases. The validity of the estimations in connection with the sampling procedures is discussed.