Orogen: X-DNA Only | DNA Science

Relationship predictions for X-DNA matches

This tool provides relationship predictions for only X Chromosome DNA (X-DNA), but works for matches who share autosomal DNA (atDNA) or who do not. X-DNA is not as useful for relationship predictions as atDNA, but this tool can be nonetheless instructive. Also, a combination of atDNA and X-DNA predictions would be more accurate than atDNA predictions alone.

Enter your shared cMs from X-DNA into the box below


Sexes of the testers

This X-DNA relationship predictor does not include population weights. For that reason, some matches will be more distant than what's suggested here. To compare these X-DNA probabilities to autosomal DNA (atDNA) probabilities, you'll want to use the unweighted atDNA predictor.

For most other atDNA relationship predictions, you'll want to use a predictor with population weights.

Recent discoveries have shown that including X-DNA in the total is better than ignoring the X-DNA amount in relationship predictions.

1C1R = 1st cousin, once removed; cM = centiMorgan.

The above probabilities assume no endogamy or other pedigree collapse. Those cases should be treated separately. For a double cousin predictor, click here.

*Parent/child and full-sibling relationships are easy to distinguish from each other or any other relationships using atDNA. Parent/child relationships consist of a half-identical match across the whole length of the genome. Full-siblings share 12.5% fully-identical regions (FIR), on average. Genotyping sites will take this into account in their relationship predictions. Trust the labels given at the original testing site if both people have their DNA there.

Probabilities are included for relationships as far back as 8C1R. Matches as low as 8 cM are allowed here. For 8 cM and higher matches in a predictor with no population weights, the most likely relationship is never a distant cousin. Instead, it's 1st cousins once removed for two female testers and great uncle/nephew for two male testers. However it's still sometimes possible that the true relationship between two matches is farther back than the most probable relationship listed, or even farther back than 8C1R.

Totals will not always add up to 100%. When more relationship types are possible, the chances of rounding errors increases. For more information about the methodology and discoveries associated with this tool, click here.

The data used for these predictions came from Caballero et al. (2019). In this case, the refined genetic map of Bhérer et al. (2017) was used as well as the crossover interference parameters of Campbell et al. (2015).