Evaluation of the forensic efficiency of ChrX markers

This section contains information about the forensic power of the corresponding ChrX markers. The formulas are listed in the table below.

Polymorphism information content (PIC) [1] and expected heterozygosity (Het) [2] were constructed for more general purposes and are valid for both AS and ChrX markers.

The mean exclusion chance (MEC) by Krueger et al. [3] was introduced for AS markers typed in trios of mother, child and putative father (MEC-Krü: formula 3). This parameter is not appropriate for ChrX markers, except in deficiency cases where the paternal grandmother can be examined instead of the putative father. Kishida et al. [4] developed a MEC for ChrX markers that includes trios with a daughter (MEC-Kis: formula 4). Comparing MEC-Krü with MEC-Kis, the latter is significantly larger. This highlights the fact that ChrX markers are more informative than AS markers for trios with a daughter.

Finally, Desmarais et al. [5] introduced formulas for the mean exclusion chance (MEC-Des) of ChrX markers in trios with daughters (formula 5) and in father-daughter duos without maternal genotype information (formula 6). MEC-Des is equivalent to MEC-Kis while MEC (formula 6) is also suitable for mother-son duos. PD-m and PD-f (formulas 7,8) are parameters for evaluating the performance of markers for forensic identification purposes in males and females, respectively.

		Formula	Ref.
1.	PIC		[1]
2.	Het		[2]
3.	MEC-Krü - AS markers - trios		[3]
4.	MEC-Kis - ChrX markers in trios with daughters		[4]
5.	MEC-Des - ChrX markers in trios with daughters		[5]
6.	MEC-duos		[5]
7.	PD-females		[5]
8.	PD-males		[5]

fi (fj): population frequency of the ith (jth) marker allele

References:

[1] Botstein D, White RI, Skolnick M, Davis RW (1980) Construction of a genetic linkage map in man using restriction fragment length polymorphisms. Am J Hum Genet 32:314-331

[2] Nei M, Roychoudhury AK (1974) Sampling variances of heterozygosity and genetic distance. Genetics 76:379-390

[3] Krüger J, Fuhrmann W, Lichte KH, Steffens C (1968) Zur Verwendung der sauren Erythrocytenphosphatase bei der Vaterschaftsbegutachtung.Dtsch Z Gerichtl Med 64:127-146

[4] Kishida T, Wang W, Fukuda M, Tamaki Y (1997) Duplex PCR of the Y-27H39 and HPRT loci with reference to Japanese population data on the HPRT locus. Nippon Hoigaku Zasshi 51: 67-69 18.

[5] Desmarais D, Zhong Y, Chakraborty R, Perreault C, Busque L (1998) Development of a highly polymorphic STR marker for identity testing purposes at the human androgen receptor gene(HUMARA). J Forensic Sci 43:1046-1049