Dugs Papers

A collection of Douglas Racionzer's thinking on a variety of topics including assignments in ethics.

Wednesday, November 15, 2006

My DNA results

GENETIC ANCESTRY TESTING REPORT
Division of Human Genetics, National Health Laboratory Service, P O Box 1038, Johannesburg, 2000
Room 303 James Gear Building, Corner of Hospital and DeKorte Streets, Braamfontein
Tel: (011) 489-9237 (Laboratory) Prof Himla Soodyall: (011) 489-9208 FAX: (011) 489-9226
MRC/NHLS/WITS HUMAN GENOMIC
DIVERSITY AND DISEASE RESEARCH UNIT
(HGDDRU)

NAME: Douglas Racionzer
SEX: Male
MtDNA analysis
MtDNA HVRI variation: 16183A-C, 16189T-C, 16223C-T,16278C-T,
16294C-T, 16390G-A
MtDNA HVRII variation: 73A-G, 143G-A, 146T-C, 195T-C, 263A-G
MtDNA haplogroup: L2a
MtDNA matches: When we searched our sub-Saharan African
database we found no identical match; closest
match differed by two base positions to 2
Bantu-speakers from South Africa.
Haplogroup information

It is possible for us to reconstruct the evolutionary history of all mtDNA lineages
found in living peoples to a common ancestor, sometimes referred to in the
popular press as “Mitochondrial Eve”. This ancestor lived in Africa, about
150,000 years ago. She lies at the root of all the maternal ancestries of every
one of the six billion people in the world. We are all her direct maternal
descendants. The various “patterns” of mtDNA sequence variation found in living
people are referred to as “haplogroups” that are defined by the presence of
certain changes (mutations) when compared to a published sequence referred to
as the reference sequence. These mutations are random and not associated with
any disease. The global pattern of distribution of mtDNA haplogroups is shown in
Figure 2 in the information sheet given to you at the time of sampling.

Of the thirty-three haplogroups recognized worldwide, thirteen can be traced to
geographic origins in Africa. MtDNA types found in African populations share
certain common features and have been assigned to haplogroup L. Haplogroup L
can be further resolved into L1, L2 and L3 (Sykes 2001). Haplogroup L2 is
divided into 4 subclades L2a through to L2d.

L2a is the most frequent and widespread mtDNA cluster in Africa. It does appear
to have an origin in West Africa and to have undergone dramatic expansion
either in southeastern Africa or in a population ancestral to present day
southeastern Africans, its distribution does suggest a signature for the Bantu
expansion (see distribution in map below). Sequences associated with this
haplogroup have been evolving for about 33,000 years (Salas et al. 2002).

The following is an extract from and article published in the American Journal of Human Genetics:
The Making of the African mtDNA Landscape
Antonio Salas,1,2,3 Martin Richards,2 Tomás De la Fe,1 María-Victoria Lareu,1 Beatriz Sobrino,1 Paula Sánchez-Diz,1 Vincent Macaulay,3 and Ángel Carracedo1
Haplogroup L2
Haplogroup L2 (figs. 6 and 7) is commonly subdivided into four main subclades, L2a through L2d (Chen et al. 2000; Pereira et al. 2001; Torroni et al. 2001). L2c cannot be distinguished from L2* without HVS-II information (325 in HVS-II) or coding-region mutations, although some of its subclades have distinctive HVS-I motifs. Among the southeastern Africans typed for this study (table 1), we found no L2* mtDNAs (in agreement with Torroni et al. 2001). The great majority belong to L2a (fig. 6), the most frequent and widespread mtDNA cluster in Africa (nearly a quarter of all indigenous types), as well as in African Americans.
We have attempted partly to disentangle the structure of L2a, retaining as irreducible on present evidence three major squares close to the root of the cluster. These reticulations link eight main clusters by single-step mutations. We assume that the main reticulations of the network are due to the existence of rapid transitions at positions 16189 and 16192 (Howell et al. 2000), which approach saturation due to the high time depth of African lineages. We also assume that position 16309 is more stable than the two known fast sites and therefore is not responsible for the main reticulations. On these grounds, clusters α1-α2-α3, as well as β1-β2-β3, might be collapsed into two main clusters, one of them with the basal motif of L2a and the other harboring the transition at 16309 (L2a1). Several instances in which 16309 must nevertheless evolve in parallel can then be read off the network.
There are two L2a clusters well represented in southeastern Africans, L2a1a and L2a1b, both defined by transitions at quite stable HVS-I positions. Both of these appear to have an origin in West Africa (as indicated by the distribution of matching or neighboring types), and to have undergone dramatic expansion either in southeastern Africa or in a population ancestral to present-day southeastern Africans. L2a1b almost certainly includes the 16192T-derived subcluster, which is exclusively present in the southeast. The very recent starbursts in subclades L2a1a and L2a2 suggest a signature for the Bantu expansions, as also suggested by Pereira et al. (2001). The L2a1a founder candidate dates to 2,700 (SE 1,200) years ago. For L2a1b there is a rather older age estimate of 8,850 years, but this has an enormous standard error (SE 4,600 years) as a result of the early 16192 branch (Pereira et al. 2001). If we assume a starlike tree by suppressing the 16192 variant (effectively assuming that this is a third founder type), the age is 5,250 (SE 1,600) years. An average age estimate, under the assumption of two founders in L2a, is 6,600 (SE 3,000) years or, under the assumption of three founders, 3,750 (SE 900) years. Thus, it appears that the founder ages for L2a are significantly older than for L1a, consistent with the phylogeographical picture, with an earlier West African origin for the L2a lineages of southeastern Africa and a more recent East African origin for the L1a lineages. Indeed, the age of the L2a founders in southeastern Africa is consistent with an origin in the earliest Bantu dispersal from the Cameroon plateau, 3,500 years ago (Phillipson 1993).
It is difficult to trace the origin of L2a with any confidence. The deepest part of L2a, represented by clusters α1-α3, is most common in East Africa. However, the diversity and TMRCA are similar in East (61,250 [SE 13,500] years) and West (54,100 [SE 17,087] years) Africa. The diversity accumulated separately in East and West Africa, estimated from the main shared founder types (and disregarding the possibility of subsequent gene flow), is again similar in the two regions, at ∼14,000 years (14,100 years [SE 5,100], and 13,800 years [SE 4,700], respectively), suggesting a separation shortly after the Last Glacial Maximum. An easterly origin for L2a also faces the following difficulties: that the other subclades of L2 (L2b, L2c, and L2d) have a clear western distribution, and that L2d diverges earlier in the mtDNA phylogeny than L2a (Torroni et al. 2001). A possible solution would be an origin for L2a somewhere between east and west, followed by dispersals in both directions along the Sahel corridor.
Haplogroups L2b, L2c, and L2d appear to be largely confined to West and western Central Africa (and African Americans), with only minor occurrences of a few derived types in the southeast. L2b also shows isolated occurrences in the east and as far north as Iberia. Therefore, an origin for all three in West and western Central Africa seems likely. Complete sequence data indicate that L2d is the oldest of the four subclades of L2, diverging before L2a, and that L2b and L2c are sister clades that diverged more recently (Torroni et al. 2001). The estimated divergence times, ranging from ∼120,000 years, for L2d, through 55,000 years, for L2a, and ∼30,000 years, for L2b and L2c, with an estimated overall age for L2 of ∼70,000 years, are consistent with this pattern. In the light of this, it is scarcely surprising that tracing its place of origin is problematic. At such an age, it seems perhaps unlikely that L2d should have diverged in West Africa, but, given the period of potential drift and extinction, the data are certainly consistent with a Central African origin. A single type in the subclade L2d1, not seen in the southeastern Africans but present at high frequency in the Bubi of Bioko, may represent a trace of this.
L2 contributes 36% (95% CR .316–.408) to the southeastern Bantu population. If we sum this with the other major southeastern haplogroups of clear West African origin, L3b and L3d, the combined contribution of a putative West African source is ∼44% (95% CR .398–.493).
(Am J Hum Genet. November 2002; 71(5): 1082–1111)


Y chromosome analysis
Two kinds of Y chromosome data were used to resolve your Y chromosome
lineage. The first involved screening for certain mutations to elucidate the Y
chromosome haplogroup (groups of lineages that are identical by descent since
they share a common defining mutation). The second involved the use of faster
evolving DNA called short tandem repeats (STRs) that we use to further resolve
the haplogroup. By screening for several of these STR markers it is possible to
derive a haplotype, a combination of the patterns observed for each region on
the Y chromosome tested.

Y chromosome haplogroup: E-M35
Haplogroup information:
Haplogroup E-M35 was one of the Y haplogroups that was common among the
Neolithic farmers from the Middle East who first brought agriculture into Europe
about 9 000 years ago. It has been estimated that the date of the most recent
common ancestor of all E-M35's is 24 000 to 27 000 years ago and that the
probable place of origin was east Africa (Cruciani et al. 2004). It is seen most
frequently along the Mediterranean coast at frequencies of 20-24% in Greece,
10-27% in Italy, and 2-11% in Spain (Semino et al. 2004). It is present at low
frequencies in Britain at 6%, in Germany at 3%, and less than 0.5% in Norway
(Capelli et al. 2003). Haplogroup E-M35 is seen at a frequency of ~ 10% in the
South African White and Jewish population.

STR profile:
Marker DYS19 DYS389I DYS389II DYS390 DYS391 DYS392 DYS393
Profile 14 14 32 24 10 11 13
Range 10-19 9-17 24-35 12-29 6-15 6-18 7-17
Marker DYS385 DYS438 DYS439
Profile 16, 17 10 12
Range 7-25 8-12 8-15

STR Matches:
We compared your Y chromosome STR profile with about 41,000 Y chromosome
haplotypes from a STR database (www.ystr.org). When using all ten markers
(both tables above) we found no identical match. However, when using 7
markers (first table) we found 10 identical matches worldwide, i.e. 4 European, 3
Latin American, 1 North American and 2 matches found in an African population.
When we searched our local database, using the first seven markers we found
no identical match; closest matches differed by one STR repeat to 2 South
Africans, i.e. 1 Jewish and 1 Coloured

References
Capelli et al. 2003. Curr Biol. 13(11):979-84.
Cruciani et al. 2004. Am J Hum Genet. 74(5):1014-22.
Semino et al. 2004. Am J Hum Genet. 74(5):1023-34.
Salas et al. 2002. Am J Hum Genet 71: 1082-1111.

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