A Case of Two Full Sisters Share Identical Genotypes on the X Chromosome

Abstract

X-chromosomal genetic markers are frequently employed in forensic parentage determination owing to their distinctive inheritance patterns. The kinship analysis revealed that two sisters who were not identical twins had identical genotypes on the X chromosome, encompassing 36 X-chromosomal short tandem repeats (X-STRs) and 29 X-chromosomal single-nucleotide polymorphisms (X-SNPs) that spanned the whole X chromosome from the p-telomere to the q-telomere. The identical X-STRs and X-SNPs in the daughters could be the result of linkage or a rare chance of occurrence. This highlights the need for careful analysis and interpretation when dealing with X chromosome markers and that in individual cases, even if two women share an allele at each locus, this does not necessarily mean that they are paternal sisters. The likelihood of random concordance due to maternal alleles must be taken into account.

Keywords

• linkage disequilibrium
• recombination
• short tandem repeats
• single-nucleotide polymorphisms
• x chromosome