...
Post A Reply
my profile
|
directory
login
|
register
|
search
|
faq
|
forum home
»
EgyptSearch Forums
»
Egyptology
»
beyoku asks: Which population is the most genetically distinct from Sub Saharans?
» Post A Reply
Post A Reply
Login Name:
Password:
Message Icon:
Message:
HTML is not enabled.
UBB Code™ is enabled.
[QUOTE]Originally posted by Troll Patrol # Ish Gebor: [QB] [QUOTE] The genetic relationships between these early modern humans and present-day human populations have not been established. [/QUOTE]--DNA analysis of an early modern human from Tianyuan Cave, China An African American Paternal Lineage Adds an Extremely Ancient Root to the Human Y Chromosome Phylogenetic Tree Copyright © 2013 The American Society of Human Genetics All rights reserved. The American Journal of Human Genetics, Volume 92, Issue 3, 454-459, 28 February 2013 [QUOTE]We report the discovery of an African American Y chromosome that carries the ancestral state of all SNPs that defined the basal portion of the Y chromosome phylogenetic tree. We sequenced ∼240 kb of this chromosome to identify private, derived mutations on this lineage, which we named A00. We then estimated the time to the most recent common ancestor (TMRCA) for the Y tree as 338 thousand years ago (kya) (95% confidence interval = 237–581 kya). Remarkably, this exceeds current estimates of the mtDNA TMRCA, as well as those of the age of the oldest anatomically modern human fossils. The extremely ancient age combined with the rarity of the A00 lineage, which we also find at very low frequency in central Africa, point to the importance of considering more complex models for the origin of Y chromosome diversity. These models include ancient population structure and the possibility of archaic introgression of Y chromosomes into anatomically modern humans. The A00 lineage was discovered in a large database of consumer samples of African Americans and has not been identified in traditional hunter-gatherer populations from sub-Saharan Africa. This underscores how the stochastic nature of the genealogical process can affect inference from a single locus and warrants caution during the interpretation of the geographic location of divergent branches of the Y chromosome phylogenetic tree for the elucidation of human origins. [...] [IMG]http://ars.els-cdn.com/content/image/1-s2.0-S0002929713000736-gr1.jpg[/IMG] [QUOTE] Figure 1. Genealogy of A00, A0, and the Reference SequenceLineages on which mutations were identified and lineages that were used for placing those mutations on the genealogy are indicated with thick and thin lines, respectively. The numbers of identified mutations on a branch are indicated in italics (four mutations in A00 were not genotyped but are indicated as shared by Mbo in this tree). The time estimates (and confidence intervals) are indicated kya for three nodes: the most recent common ancestor, the common ancestor between A0 and the reference (ref), and the common ancestor of A00 chromosomes from an African American individual and the Mbo. Two sets of ages are shown: on the left are estimates (numbers in black) obtained with the mutation rate based on recent whole-genome-sequencing results as described in the main text, and on the right are estimates (numbers in gray) based on the higher mutation rate used by Cruciani et al.6[/QUOTE][IMG]http://ars.els-cdn.com/content/image/1-s2.0-S0002929713000736-gr2.jpg[/IMG] [QUOTE]We also estimated the level of variation among nine A00 lineages (i.e., including one additional Mbo individual) by using a battery of 95 Y-STRs for which all individuals had no missing data; (Table S2). A median-joining network28 shows that the African American A00 lineage is 11 mutational steps from the nearest Mbo and that the maximum difference between any pair of Mbo is nine steps (Figure 3 and Table S2). On the basis of these levels of within- and between-group variation, we calculated a second divergence time estimate of 564–2,697 years (Table 1) by assuming a mean Y-STR mutation rate of 1.32 × 10−4 and 2.76 × 10−5 per year, respectively.29 and 30 [/QUOTE][IMG]http://ars.els-cdn.com/content/image/1-s2.0-S0002929713000736-gr3.jpg[/IMG] [QUOTE] Figure 3. Median-Joining Network of A00 HaplotypesThe network is based on haplotypes (constructed with 95 Y-STRs) of eight Mbo and an African American (AA) individual. All mutations are assumed to be single step and were given equal weight during the construction of the network. Marker names are indicated without “DYS” at the beginning. [/QUOTE][CODE] Table 1. Pairwise and Average STR-Based Estimates of TMRCA for A00 Chromosomes TMRCA (Years) Mbo 52 Mbo 159 Mbo 160 Mbo 170 Mbo 173 Mbo 183 Mbo 186 Mbo 199 African American Average with Mboa Mbo 52 - 80 120 159 239 159 199 120 478 154 Mbo 159 381 - 120 159 239 159 199 120 478 154 Mbo 160 572 572 - 120 199 199 239 159 439 165 Mbo 170 763 763 572 - 239 239 279 199 478 199 Mbo 173 1,144 1,144 953 1,144 - 319 359 279 399 268 Mbo 183 763 763 953 1,144 1,526 - 120 120 558 188 Mbo 186 953 953 1,144 1,335 1,716 572 - 159 598 222 Mbo 199 572 572 763 953 1,335 572 763 - 518 165 African American 2,288 2,288 2,098 2,288 1,907 2,670 2,860 2,479 - 564 Average with Mbob 736 736 790 953 1,280 899 1,062 790 2,697 - [/CODE]We obtained point estimates of the TMRCA of two haplotypes by dividing the estimate of the number of mutational steps separating the haplotypes (as inferred from the network) by twice the mutational rate per STR and by the number of STRs scored in both haplotypes. Values above and below the diagonal separation correspond to estimates obtained with the high and low mutation rates, respectively (see text). The following abbreviation is used: TMRCA, time to the most recent common ancestor. [/QUOTE] http://www.cell.com/AJHG/retrieve/pii/S0002929713000736 Full paper: http://ac.els-cdn.com/S0002929713000736/1-s2.0-S0002929713000736-main.pdf?_tid=f139fbc0-27bb-11e3-a241-00000aab0f6c&acdnat=1380317571_68a0d709ae6f30ea5769e6cb13903b3a [/QB][/QUOTE]
Instant Graemlins
Instant UBB Code™
What is UBB Code™?
Options
Disable Graemlins in this post.
*** Click here to review this topic. ***
Contact Us
|
EgyptSearch!
(c) 2015 EgyptSearch.com
Powered by UBB.classic™ 6.7.3