Haplogroup
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A haplogroup is a combination of alleles at different chromosomes regions that are closely linked and that tend to be inherited together. It is a group of individual organisms which, in terms of molecular evolution, share a common ancestor – a genetic line of descent demonstrated by a particular single nucleotide polymorphism (SNP) mutation. Because a haplogroup consists of similar haplotypes, it is usually possible to predict a haplogroup from haplotypes.
Haplogroups pertain to a single line of descent, usually dating back thousands of years. As such, membership of a haplogroup, by any individual, relies on a relatively small proportion of the genetic material possessed by that individual.
Each haplogroup originates from, and remains part of, a preceding single haplogroup (or paragroup). As such, any related group of haplogroups may be precisely modelled as a nested hierarchy, in which each set (haplogroup) is also a subset of a single broader set (as opposed, that is, to biparental models, such as human family trees).
Haplogroups are normally identified by an initial letters of the alphabet, and refinements consist of additional number and letter combinations, such as (for example) A → A1 → A1a.
In human genetics, the haplogroups most commonly studied are Y-chromosome (Y-DNA) haplogroups and mitochondrial DNA (mtDNA) haplogroups, both of which can be used to define genetic populations. Y-DNA is passed solely along the patrilineal line, from father to son, while mtDNA is passed down the matrilineal line, from mother to offspring of both sexes. Neither recombines, and thus Y-DNA and mtDNA change only by chance mutation at each generation with no intermixture between parents' genetic material.
See also
- International HapMap Project
- Molecular evolution
- Molecular phylogenetics
- Haplotype
- Human evolutionary genetics
- Race (biology) / Race (human classification)
- Genetic genealogy
- Genealogical DNA test
- Genetics
- List of genetic genealogy topics
- List of haplogroups of notable people
- Paragroup
