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Ingenetics, asubclade is a subgroup of ahaplogroup.[1]
Althoughhuman mitochondrial DNA (mtDNA) andY chromosome DNA (Y-DNA) haplogroups and subclades are named in a similar manner, their names belong to completely separate systems.[2]
mtDNA haplogroups are defined by the presence of a series ofsingle-nucleotide polymorphism (SNP)markers in thehypervariable regions and thecoding region ofmitochondrial DNA. They are named with the capital letters A through Z, with further subclades named using numbers and lower case letters.[2][3][4]
Y-DNA haplogroups are defined by the presence of a series of SNP markers on theY chromosome. Subclades are defined by aterminal SNP, the SNP furthest down in the Y chromosome phylogenetic tree.[5]
TheY Chromosome Consortium (YCC) developed a system of naming major human Y-DNA haplogroups with the capital letters A through T, with further subclades named using numbers and lower case letters (YCC longhandnomenclature). YCC shorthand nomenclature names Y-DNA haplogroups and their subclades with the first letter of the major Y-DNA haplogroup followed by a dash and the name of the defining terminal SNP.[6] Y-DNA haplogroup nomenclature is changing over time to accommodate the increasing number of SNPs being discovered and tested, and the resulting expansion of the Y chromosome phylogenetic tree. This change in nomenclature has resulted in inconsistent nomenclature being used in different sources.[7] This inconsistency, and increasingly cumbersome longhand nomenclature, has prompted a move towards using the simpler shorthand nomenclature.
A terminal SNP determines the terminal (final) subbranch on the Y-DNA Tree to which someone belongs.