Dependency of concordance probability on gene frequencies in genetic systems for the diagnosis of twin zygosity. A graphical presentation enabling the rapid, optimal choice of genetic system.

The dependency of probabilities of phenotypic concordance of gene frequencies in three-allele genetic systems is presented. A graphical display enables the rapid comparison of the relative effectiveness of different systems, taking into account dominance relationships within each genetic system. Four or more allele systems can also be approximated, while two-allele systems are considered to be special cases of three-allele ones.