Y-chromosomal Adam

Y-Chromosome Adam is a term from population genetics for the common paternal ancestor of all men living today. For genetic genealogy, it is useful as the root of the human Y-DNA tree.

Linkage disequilibrium

Linkage disequilibrium describes any case in population genetics where the frequency of two alleles being found together implies a non-random association. That is, the odds of both alleles happening together is not random.


Genetic genealogy DNA test kits use saliva samples to collect DNA from dead cells inside our mouths. Test kits from Ancestry.com and 23andMe use spit collection tubes while Living DNA and FamilyTreeDNA use swabs.


An X-match is a genetic match that shares a relevant DNA segment on the X-chromosome. Because the X-chromosome follows a different inheritance pattern than autosomal DNA, X-matches are highly significant for some genealogy applications.

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