Formulas developed specifically for ChrX markers in the context of kinship testing are listed in Table 7.1. They can be used to calculate the gain of the concerning marker in usage for kinship testing in dependence of the allele distribution in a certain population. In trios involving a daughter, ChrX markers are more efficient than AS markers. This fact is reflected by the formulas for calculation of MEC(I) for AS markers (Krüger et al., 1968) and MEC(II) (Kishida et al., 1997) and MEC(III) (Desmarais et al., 1998). MEC(III) is equivalent to MEC(II). MEC(I) for AS is not suitable for ChrX markers except for deficiency cases in which the paternal grandmother is investigated instead of the alleged father. If MEC(I) is compared to MEC(II) and MEC(III), the latter are consistently larger. Finally, Desmarais et al. (1998) introduced formulas for the mean exclusion chance of ChrX markers involving father/daughter duos lacking maternal genotype information, MEC(IV), which is also appropriate for maternity testing of mother/son duos.
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