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In the study of molecular evolution, a 'haplogroup' is a large group of haplotypes, which are series of alleles at specific locations on a chromosome.

In human genetics, the haplogroups mostly 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 has the advantage of being passed solely along the patrilineal line, while mtDNA is passed solely on the matrilineal line.

Classifications of human haplogroups of either sort based on genetic markers has been rapidly evolving over the past several years as new markers are found.

Haplogroup population genetics

It is usually assumed that there is little natural selection for or against a particular haplotype mutation which has survived to the present day, so apart from mutation rates (which may vary from one marker to another) the main driver of population genetics affecting the proportions of haplotypes in a population is genetic drift - random fluctuation caused by the sampling randomness of which members of the population happen to pass their DNA on to members of the next generation of the appropriate sex. This causes the prevalence of a particular marker in a population to continue to fluctuate, until it either hits 100%, or falls out of the population entirely. In a large population with efficient mixing the rate of genetic drift for common alleles is very slow; however, in a very small interbreeding population the proportions can change much more quickly. The marked geographical variations and concentrations of particular haplotyes and groups of haplotypes therefore witness the distinctive effects of repeated population bottlenecks or founder events followed by population separations and increases.

The lineages which can be traced back from the present will not reflect the full genetic variation of the older population: genetic drift means that some of the variants will have died out. With a full mtDNA sequence currently costing over $1000 commercially as of 2006, few data are yet available. Haplotype coalescence times and current geographical prevalences both carry considerable error uncertainties.

Human Y-chromosome DNA haplogroups

Y-DNA

Y-chromosomal Adam is the name given by researchers to the male who is the most recent common patrilineal (male-lineage) ancestor of all living humans.

Major Y-chromosome haplogroups include:

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Groups without mutation M168

• Haplogroup A (M91)

• Haplogroup B (M60)

Groups with mutation M168

• Haplogroup C (M130)

• Haplogroup D (M174)

• Haplogroup E (M96)
  • Haplogroup E3a (M2)
  • Haplogroup E3b (M35)
• Haplogroup F* (M89)

Groups descended from Haplogroup F*

• Haplogroup G (M201)

• Haplogroup H (M52)

• Haplogroup I (M170)

• Haplogroup J (12f2.1)
  • Haplogroup J1
  • Haplogroup J2 (M172)
  • Haplogroup J*

• Haplogroup K (M9)
  • Haplogroup K2 (M70)

Groups descended from Haplogroup K

• Haplogroup L (M20)

• Haplogroup M (M4)

• Haplogroup N (LLY22g)

• Haplogroup O (M175)
  • Haplogroup O3 (M122)

• Haplogroup P (M45)

• Haplogroup Q (M130)
  • Haplogroup Q3 (M242)

• Haplogroup R (M207)
  • Haplogroup R1a1 (M17)
  • Haplogroup R1b (M343)
  • Haplogroup R2 (M124)

Human mitochondrial DNA haplogroups

MtDNA

For a graphical depiction of haplogroup branching, see the http://www.stats.gla.ac.uk/~vincent/images/skeleton07-08-02.jpg mtDNA haplogroup skeleton.

Mitochondrial Eve is the name given by researchers to the woman who is the most recent common matrilineal (female-lineage) ancestor of all living humans.

Defining populations

Map of human race migration, according to mitochondrial DNA.

Haplogroups can be used to define genetic populations and are often geographically oriented. For example, the following are common divisions for mtDNA haplogroups:

• West Eurasian: H, T, U, V, X, K, N, I, J
• Sub-Saharan African: L, L1, L2, L3, L3*
• East Asian: A, B, C, D, E, F, G (note: C, D, E, and G belong to macro-haplogroup M)
• Native American: A, B, C, D, and sometimes X

See also

• molecular evolution
• molecular systematics
• molecular phylogeny
• haplotype
• genetic genealogy
• genealogical DNA test
• genetics
• * (haplogroup)

External links

General

• http://www.geocities.com/refuting_kemp/gene_intro.html Y Chromosome and mtDNA haplogroups

News

• http://www.springerlink.com/media/53f7mgywmp4qtqrgtav0/contributions/f/1/4/2/f142j25785572821_html/fulltext.html Indian maternal gene pool, Journal of Human Genetics
• http://dienekes.blogspot.com/ Dienekes' Anthropology Blog frequent highlights of new results.

• http://ycc.biosci.arizona.edu/ Y Chromosome Consortium
• http://www.isogg.org/tree/index.html ISOGG Y-DNA Haplogroup Tree 2006
• http://www.dnaheritage.com/ysnptree.asp DNA Heritage's Y-haplogroup map
• https://home.comcast.net/~whitathey/predictorinstr.htm Haplogroup Predictor
• The Y Chromosome Consortium (2002), http://www.genome.org/cgi/content/full/12/2/339 A Nomenclature System for the Tree of Human Y-Chromosomal Binary Haplogroups, Genome Research, Vol. '12'(2), 339-348, February 2002. (Detailed hierarchical http://www.genome.org/cgi/content-nw/full/12/2/339/F1 chart has conversions from previous naming schemes)
• http://dnaconsultants.com/images/links/49-conversion.pdf DNA Consulting's Conversion Chart for Male Haplogroups (PDF)
• Semino et al (2000), http://hpgl.stanford.edu/publications/Science_2000_v290_p1155.pdf The Genetic Legacy of Paleolithic Homo sapiens sapiens in Extant Europeans, Science, Vol '290' (paper which introduced the "Eu" haplogroups).