DXS6797 contains two STRs which can be easily haplotyped in both sexes.
DXS6797 is a complex X-chromosomal locus which contains two variable short tandem repeats (STRs) (motif ATCT) separated by 128 non-polymorphic nucleotides. The two STRs can be cleaved apart by Taq I digestion. Conventionally, DXS6797 is typed by measuring the overall amplicon length, providing only eight alleles [polymorphism information content (PIC) 0.733, mean exclusion chance (MEC) 0.712]. Separate amplification would increase the discrimination but obscure the haplotype constellation in females. Therefore, we proceed by amplifying the whole sequence containing both repeats (DXS6797 I and DXS6797 II) using a Fam-labelled forward primer and a Tamra-labelled reverse primer. We then measure the length of the entire double-labelled amplicon and a Taq-I-digested aliquot to infer, for both males and females, compound haplotypes consisting of DXS6797 I and DXS6797 II repeat length. This procedure has the potential to provide 42 DXS6797 haplotypes. If the crossover rate between both STRs is assumed to be <1.5x10(-6), DXS6797 haplotypes could be used for kinship testing like STR alleles. In our German sample (780 X chromosomes), we determined 27 haplotypes (PIC 0.842, MEC 0,834) and in 220 meioses, we found no new mutations.
Poetsch
Micaela
M
Institut für Rechtsmedizin, Ernst Moritz Arndt-Universität, Kuhstrasse 30, 17489 Greifswald, Germany.
Repenning
Antje
A
Lignitz
Eberhard
E
Kuhlisch
Eberhard
E
Szibor
Reinhard
R
D000293:Adolescent; D000328:Adult; D041321:Chromosomes, Human, X; D016172:DNA Fingerprinting / Q000379:methods*; D017931:DNA Primers; D005260:Female; D005787:Gene Frequency; D008040:Genetic Linkage; D005828:Genetics, Population; D005858:Germany; D006239:Haplotypes; D006801:Humans; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D020080:Tandem Repeat Sequences; D019914:Taq Polymerase / Q000235:genetics
D017931:DNA Primers; D019914:Taq Polymerase