Haplogroup

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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 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 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 have been rapidly evolving over the past several years as new markers are found.

Contents

[edit] 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. The price of full mtDNA sequence tests has limited the availability of data. Haplotype coalescence times and current geographical prevalences both carry considerable error uncertainties.

[edit] Human Y-chromosome DNA haplogroups

Main article: Human Y-chromosome DNA haplogroup

Human Y chromosome DNA (Y-DNA) haplogroups are lettered A through R, and are further subdivided using numbers and lower case letters. Y chromosome haplogroup designations are established by the Y Chromosome Consortium.

Human Y-chromosome DNA (Y-DNA) haplogroups
Y-most recent common ancestor
|
A |
B |
C | F
D E G H | K
I J L M | P
N O Q R

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, and their geographical regions of occurrence (prior to the recent european colonization), include:

[edit] Groups without mutation M168

[edit] Groups with mutation M168

(mutation M168 occurred ~50,000 bp)

  • Haplogroup C (M130) (Australia and surrounding areas, Siberia, North America)
  • Haplogroup D (M174) (Tibet, Japan, especially the Ainu of Japan, the Andaman Islands)

[edit] Groups with mutation M89

(mutation M89 occurred ~45,000 bp)

[edit] Groups with mutation M9

(mutation M9 occurred ~40,000 bp)

  • Haplogroup K (no additional major mutations) (New Guinea, Australia)
    • Haplogroup K2 (M70)

[edit] Groups with mutation M45

(mutation M45 occurred ~35,000 bp)

[edit] Human mitochondrial DNA haplogroups

Main article: Human mitochondrial DNA haplogroup

Human mitochondrial DNA (mtDNA) haplogroups are lettered A, B, C, D, E, F, G, H, I, J, K, L, L1, L2, L3, M, N, T, U, V, W X, and Z.

Human mitochondrial DNA (mtDNA) haplogroups
  mt-most recent common ancestor    
L0   L1  
L2 L3  
  M   N
M1 CZ D E G Q A I W X   R   N1 N2 Y
C Z B JT F U
J T K pre-HV
HV
H V


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.

[edit] Defining populations

Map of human race migration, according to mitochondrial DNA.
Enlarge
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, W[1]
  • 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

The mitochondrial haplogroups are divided into 3 main groups, which are designated by the 3 sequential letters L, M, N. Humanity first split between the L group and the rest, and then the M and N groups split. The L type consists of africans, and especially sub-saharan africans. The M type consists of most east asians and many amerindians that descend from them, consisting of the minority of north and central amerindians and the majority of south amerindians. The N type consists of everyone else, including people from europe and the vicinity of europe, some east asians, many amerindians (consisting of the majority of north and central amerindians and the minority of south amerindians) that descend from north central asians, australian aboriginies, and polynesians.

Within the N group is the large R group, which contains many haplogroups within it. The R type consists of the vast majority of europeans and middle easterners, polynesians, some australian aboriginies, some east asians, and some amerindians. In contrast, the people of the N group that do not belong to the R group consist of the majority of australian aboriginies, the majority of north and central amerindians, and some east siberians.

The haplogroups within the R group consist of 2 sets of haplogroups, one which occurs in and around europe, and consists of haplogroups HV / H / V, J / T, and U / K, and the other which occurs in and around southeast asia, and consists of haplogroups R, B, F, and P.

[edit] References

  1. ^ Loogvali et al, 2004

[edit] See also

[edit] External links

[edit] General

[edit] News

[edit] all DNA haplogroups

[edit] Y chromosome DNA haplogroups

[edit] Mitochondrial DNA haplogroups

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