Tuesday, January 29, 2008

RFLPs: Lucotte et al., A case study — Pt. 2

Continuing with Lucotte et al. 2006, North African Berber and Arab Influences in the Western Mediterranean Revealed by Y-Chromosome DNA Haplotypes.

Link to the first part of this topic:
RFLPs: Lucotte et al., A case study — Pt. 1[clickable]

There is the question of haplotype V corresponding to more than one binary marker—which is why it is important for one to understand the *context* of the specific study in question, rather than assume that one group of researchers' context per designator is the same as the other. Many a times, researchers use a standardized designation like the Y Chromosome Consortium nomenclature, applying the same context to facilitate cross-reference between researchers, and hence, compare the results at hand, but not every researcher adheres to the most popular standardized nomenclature system—some researchers use one or another system of nomenclature, dependent on the methods applied to discern haplotypic differentiation.

From what the present author can tell, Lucotte et al. didn't run their haplotypes for binary markers for the earlier studies, as exemplified in their 2001 study in "A case study — Pt. 1", but given that Lucotte et al. this time around [i.e. in the present study] proclaimed to have not only used the same sequencing methods used by them in the earlier studies [namely the 2001 and 2003 studies for example], but also the DNA polymerase chain reaction used by Underhill et al. to test for binary markers M81 and M78, presumably using samples already tested by Lucotte et al. in previous studies, they were able to verify that Lucotte et al.'s 2001 and 2003 haplotype V [which they deemed to be 'a characteristic Berber haplotype' and ' of predominantly Berber origin'] were mainly M81 chromosomes, after having further discerned haplotype V into at least two discernable groups: Vb and Va, using Gonçalves et al.'s PCR method. All the Moroccan bearers of the sub-group Vb, turned out to be M81 carriers, including *all* the 'Berber' designated speakers of this bunch and 21 of the 59 'Arab' designated North Africans; the remaining 38 'Arab' designated north African bearers of the sub-group Va either tested positive for M78 or they didn't. To be specific, 31 of the 38 Arabic speaking North African bearers of haplotype V [sub-group Va] tested positive for M78, while the rest didn't. This results confirm the sub-group Vb to be M81, and Va to be partly M78. Going by this, the majority of what Lucotte et al. refer to as a 'characteristic Berber haplotype', are M81 chromosomes.

In that Lucotte et al.'s haplotype V appears to be largely of M81 [all Vb subgroups in the intro study] and partly M78 [sub-group Va], with the remaining [sub-group Va] yet to be identified by other markers, it is obviously associated with E3b macrohaplogroup. Additionally, according to Keita, haplotype XI also turns out to be Hg E3b affiliated. Thus, alerting oneself to the context at hand, is warranted!

As to the question of whether the authors in the present study were able to genetically differentiate Moroccan "Berbers" and "Arabs" into distinct genealogical camps, the answer is that they were probably going by self-ethnic identifications of the contributors of the samples in question. Apparently much of north African populations were really 'Arabized' populations, not original ethnic Arabs. However, as the present author noted before, there is something to be discerned here:
  • All* subgroup Vb individuals are either "Berber" identified Tamazight individuals [47 individuals] or what appears to be "Arabized" Tamazight individuals [21 individuals], testing positive for E-M81, whereas...
  • ...out of the 38 remaining "Arabic" identified individuals who tested positive for the subgroup Va, 31 turned out to be positive for E-M78. The remaining 7 individuals of this 38 "Arabic" identified individuals didn't test positive for either E-M81 or E-M78. Those individuals *could* [but not necessarily] possibly turn out positive for a non-M78 and non-M81 marker like "R1a"; however, **if** J happens to have the same combination of RFLPs , then it could well be a possible candidate here, as it is the next frequent paternal line which isn't M35 derived, but still quite less frequent than the aboriginal E-M81 marker. Other non-M81 and non-M78 E-M35 [E3b] derived lineages could just as well still be a candidate.
  • Four Moroccan "Berber" individuals out of the 51 tested, appear to be unaccounted for here. They probably fell into the Va subgroup, and likely didn't test positive for either E-M81 or E-M78. These individuals could just as well test positive for the aforementioned non-M78 and non-M81 possible candidates.
In any case, non-M81 and non-M78 lineages appear to be in the minority. The majority of Moroccan "Berbers" are M81, while the majority of the Moroccan "Arabs" are largely of subgroup Va E-M78 lineage [31 individuals], but carry a significant amount of subgroup Vb E-M81 [21 individuals]. So clearly, the "Berber" group, while they share lineages [largely E-M81] with their Moroccan "Arab" counterparts, can clearly be discerned from the said "Arab" counterparts, in that the later seems to have relatively more M78 lineages, as well as relatively more non-M81 subgroup Va lineage [7 individuals] than their "Berber" identified counterparts [possibly the unaccounted for 4 "Berber" individuals].

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