Y-DNA Haplotypes From Genealogical DNA Tests
Unlike other chromosomes, Y chromosomes do not come in pairs. Every human male has only one copy of that chromosome. This means that there is no lottery as to which copy to inherit, and also (for most of the chromosome) no shuffling between copies by recombination; so, unlike autosomal haplotypes, there is effectively no randomisation of the Y-chromosome haplotype between generations. A human male should largely share the same Y chromosome as his father, give or take a few mutations.
In particular, the Y-DNA represented as the numbered results of a Y-DNA genealogical DNA test should match, barring mutations. Within genealogical and popular discussion, this is sometimes referred to as the "DNA signature" of a particular male human, or of his paternal bloodline.
Read more about this topic: Haplotype
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