Paternity testing in trios and duos

Paternity cases involving the common trio constellation of mother, offspring and alleged father can usually be solved with AS STRs alone, and do not seem to require any additional or alternative markers. When father/son relationships are to be tested, ChrX markers can contribute nothing anyway. However, when father/daughter relationships are in question it may be worthwhile including ChrX markers in testing. This is especially the case when difficult-to-analyse template materials are involved, such as DNA from exhumed skeletons, historical or prehistorical samples, etc. Despite primer sets for typing degraded DNA now being available (Hellmann et al., 2001; Wiegand and Kleiber, 2001; Asamura et al., 2006; Meissner et al., 2006), in such instances sufficient statistical power has to come from a small number of low-size STRs. Fortunately, ChrX STRs are normally characterized by relatively high MECs, even at a low to medium degree of polymorphism (Table 7.3). In those contexts, ChrX markers may be superior to AS markers in some instances. As an example I would like to mention a case that we have solved recently. We were requested to prove a father /daughter relationship by typing only the daughter's and the alleged father's saliva. The paternal saliva trace was taken from a stamp licked 30 years ago. The paternity likelihood could be established to be 99.93 by DXS8378-DXS7132, HPRTB and DXS7423 alone. Autosomal systems had contributed only little in solving this question.

Table 7.3 Comparison of the mean exclusion chance (MEC) of short amplicon STRs located at ChrX and autosome (AS) markers. For definition MEC (I)and MEC (II) see Table 1

ChrX marker

Mini STR product size

Heta

MEC(I)b

MEC(II)c

Was this article helpful?

0 0

Post a comment