Closed apriha closed 6 years ago
Ancestry's chromosome 25 seems to consist of PAR SNPs from both the X and Y chromosomes... Therefore, those SNPs can't be easily merged into chromosome X or Y without looking up the SNP in dbSNP and identifying the proper chromosome with the SNP's position.
For males, 23andMe reports two alleles for PAR regions, and one allele for the non-PAR region. Ancestry and FTDNA report two alleles for both the PAR and non-PAR regions. Therefore, for now, double all single X chromosome alleles.
In the future, perhaps the PAR regions can be identified, and for males, doubled X chromosome alleles in the non-PAR region can be converted to single alleles. This would mean males could theoretically have two chromosome matches on the X chromosome (in the PAR regions)...
Two chromosome matches on the X chromosome in the PAR regions for males is now handled; see d6b69313f79d9061f0a9e2023db199bcd03f4bf8.
PAR SNPs are now assigned to the X and Y chromosomes based on position; see 1313da4a1ec291288287113f91027b356b8766fb.