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In genetics, a subclade is a subgroup of a haplogroup. Subclades are often referred to in genealogical DNA tests of human mitochondrial DNA haplogroups and human Y-chromosome DNA haplogroups, where they represent subbranches of major branches on the human family tree.
Although human mitochondrial DNA (mtDNA) and Y chromosome DNA (Y-DNA) haplogroups and subclades are named in a similar manner, their names belong to completely separate systems.
mtDNA haplogroups are defined by the presence of a series of single-nucleotide polymorphism (SNP) markers in the hypervariable regions and the coding region of mitochondrial DNA. They are named with the capital letters A through Z, with further subclades named using numbers and lower case letters.
Y-DNA haplogroups are defined by the presence of a series of SNP markers on the Y chromosome. Subclades are defined by a terminal SNP, the SNP furthest down in the Y chromosome phylogenetic tree. The Y 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 longhand nomenclature). 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. 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. This inconsistency, and increasingly cumbersome longhand nomenclature, has prompted a move towards using the simpler shorthand nomenclature.
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Y-chromosome DNA (Y-DNA) haplogroups are the major branches on the human paternal family tree. Each haplogroup has many subbranches. These are subclades.
- "Understanding Results: mtDNA: How are mitochondrial DNA (mtDNA) Haplogroups named?". Family Tree DNA. Retrieved 3 April 2013.
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A terminal SNP determines the terminal (final) subbranch on the Y-DNA Tree to which someone belongs.
- "Understanding Results: Y-DNA Single Nucleotide Polymorphism (SNP): How are haplogroups and their subclades named?". Family Tree DNA. Retrieved 31 March 2013.
- "Understanding Haplogroups: How are the haplogroups named?". Family Tree DNA. Retrieved 31 March 2013.