希腊常染色体DNA

希腊遗传特征通过时间的持久性的一个显着的示范可以发现 [1]. 右边的图是在欧洲变化的第四主成分，并显示在希腊为中心的强烈克莱恩. 不仅是希腊的传统遗传检测的清楚今天, 但它不仅是希腊人检测的, 但部分希腊血统的他们所有的邻国人民:

人类种群的遗传亲和力可以通过检查大量多态性的确定. 举个例子, 阿尤等人. [2] 使用 182 三- 和四常染色体微卫星, 这使他们能够创建基于d以下的树_如 所采样的群体之间的遗传距离. 很显然，希腊人人口的高加索集群中属于 (从包含“北欧”到“Burusho”组图), 并且可以清晰地从亚洲/大洋洲/美国簇区分 (“柬埔寨”到“玛雅印第安人”), 更来自非洲组 (“散”到“扎伊尔俾格米“).

常染色体DNA的现代研究依赖于大量的单核苷酸多态性的研究 (单核苷酸多态性), 即, 在遗传密码的单个字母的变化. 最近的一项研究 [3] 使用 10,000 这样的多态性研究欧洲人群的遗传结构, 包括希腊人的样品. 两种不同的技术被用来: 主成分分析 (PCA) , 该发现总结遗传数据的变化是最重要的方面, 和结构的广泛使用基于模型的聚类程序, 该分配个人K个不同簇的.

结构运行的结果如下图所示.

 

对于集群中的每个数 (K), 每个簇被分配一个颜色. 从所研究的人群每个单独对应于垂直线, 并且由在不同的簇的不同的比例. 我们注意到，希腊个人属于欧洲主要-西亚，北非 (簇) 集群在K最多 5. 在K = 6一 “地中海” 小集群 (绿色) emerges which encompasses particularly populations bordering the Mediterranean as well as Armenians. 特别是, we observe that there is no visible contribution of the East Eurasian (Mongoloid) pink cluster or of Sub-Saharan African (Negroid) red cluster.

The results of the PCA for the first two principal components are shown below.

 

Each bar corresponds to a population, and its width covers the variability of the different sampled individuals within each population. The first principal component (PC1) separates Sub-Saharan Africans (Mende and Burunge) from Eurasians. The second principal component (PC2) separates Mongoloids and East Indians (Altai, Brahmin, and Mala) from other populations. In both, it is evident that the Greek individuals exhibit a typically West Eurasian (Caucasoid) genomic profile.

While the above studies have examined global population structure, 最近的研究侧重于发掘更致密欧洲血统本身种群内. 举个例子 [4] 研究欧裔美国人使用的祖先 583 SNP标记. 作者确定，欧美变化的主要特点是沿东南 - 西北轴clinal, 这证实卡瓦利-斯福扎的上述工作的裁断 [1] 基于经典标志. 第二个最显着的特点分开德系犹太人东南欧洲. 这项研究的希腊个人, 像意大利同行具有典型特征东南部, 并明确从德系犹太人分离.

 

另一项研究, [5] 考虑更大数目的SNP的, 具有相似的结果. 再来一次, 变化的主要特点从北欧分离的人口和那些来自南欧, 而第二主南欧和德系犹太人之间区分. 希腊个人是最接近于意大利人的.

 

 

另一项研究 [6] 研究了超过 2,500 欧洲人使用500000-标记的Affymetrix芯片; 这是最广泛，最详细的欧洲常染色体变异的抽样尚未. 作者认为，在欧洲南部观测杂和连锁不平衡的水平是从南方出发向北解决非洲大陆的一致. 欧洲人形成, 芬兰人除外, 遗传连续性. 各民族集群的成员一起, 并与相邻基团部分地重叠, 但可以完全从更遥远的ones.These结果基因区别表明两者欧洲基因库的相对同质化, 但也是事实，即它们可以沿地域和民族甚至强烈线条区分转基因.

 

 

该研究纳入的样本 51 希腊北部. 很明显，这些希腊人 (标志着EL), 形成均匀的簇, 他们没有落在集群的其他族群形成的中间. 一些前南斯拉夫人 (标志着YU) 不要落在希腊簇的中部，, 然而. 这些前南斯拉夫人, 还有两个意大利组 (IT1和IT2) 形成希腊人’ 亲缘邻居. 南斯拉夫人是希腊人和捷克和波兰之间, 与他们同时具有土著巴尔干和非巴尔干斯拉夫起源一致; 意大利人是希腊人和西班牙人之间, 与具有地中海贡献他们的一致, 这可能是由于农民新石器时代, 或古 (例如. 希腊或伊特鲁里亚) colonists.

Shortly after the previous study appeared, another article [7] used the same 500K Affymetrix chip over a sample of 3,192 individuals, 包括 8 Greeks. While many of the sampled populations are represented by a small number of individuals, thus making generalization more difficult, it is evident that the first two principal components bear an even stronger relationship to the geographical map of Europe. This was probably made possible by the inclusion of a wider range of populations, including many from eastern Europe.

 

 

With the caveat of the small population sample numbers, these results are fairly consistent with those of the previous study. Greeks (GR) are once again between their northern neighbors (especially Albanians (AL), Slavomacedonians (MK), Bulgarians (BG), Romanians (RO), and Kosovars (KS)) and Italians (IT). Greek Cypriots (CY) and Turks (TR) also frame the Greek sample on a more southern and eastern direction respectively. The Greeks’ closest neighbors appear to be their immediate northern neighbors, as well as some of the Italians who otherwise appear to be quite variable, some of them being more similar to their Central European neighbors; Northern Balkan Slavic populations (Slovenians (SI), Croats (HR), Bosnians (BA) appear more distant in the direction of Central and Eastern European Slavs.

Studies such as the above [4-7] have shown that in the first two principal components individuals from different European groups tend to cluster with each other. 然而, these components capture only part of the overall genetic variation: the most salient part that is associated with geography and ethnicity. A new study [8] investigated the overall genetic similarity of individual Europeans, using the dataset also used by [6]. For each individual, 一个 “best overall match” (BOM), 即, the individual most similar to him was calculated over all the markers. The results are shown in the table below:

Each row in this table shows the origin of these BOMs. As the authors note “in a considerable proportion of cases (76.0%), the BOM of a given individual, based on the complete marker set, came from a different recruitment site than the individual itself“. 举个例子, the Finnish (FI) sample consists of 47 individuals: 39 of them have a BOM that is also a Finn, while 1, 4, 和 3 have a Norwegian (NO), German (DE1), and Polish (PO) best match. It is important to note how sample sizes affect these numbers: there are 47 out of 2,457 Finns in the total sample (1.9%). 因此, if Finns were indistinguishable from other Europeans, then it would be expected that only about 0.9 of them (1.9% 的 47) would have a Finnish BOM. 因此, the fact that 39 of them do is highly significant (43 times higher than chance). 但是, the observation remains valid that a member of a particular group may have a “genetic look-alike” from a different group.

Turning to Greeks (EL, recruited in northern Greece), we see that they have BOMs from Norway, Sweden, the UK, 丹麦, the Netherlands, 德国, Austria, Switzerland, 意大利, and Greece. Conversely, the BOMs of some Dutch, Spanish, Italian, and Greek individuals is a Greek. Overall, the Greek sample consists of 51 individuals, and hence one expects (by chance) that only 1.1 of them would have a Greek BOM. 因此, Greeks have a 7-fold higher than random chance of having a fellow Greek as their BOM. Different European groups vary substantially in this: the aforementioned Finns seem to be most distinct, with most of them being more similar to a co-ethnic than to any other Europeans. Other groups seem to be less so; for example no Austrians (AT) have a fellow Austrian BOM.

The overall BOMs of the Greek individuals is also noteworthy because no matches are observed between Greeks and Eastern Europeans or vice versa. This probably indicates the absence among Greeks of many substantially “Slav-like” individuals; individual Greeks may have “genetic look-alikes” in distant Britain or Scandinavia, but none at all in Eastern Europe. 事实上, they have a greater-than-random number of matches only with the large German sample (DE1) from Kiel, which probably indicates the substantial heterogeneity of this sample, whose members serve as close matches to many European ethnic groups. The study also includes in its supplementary material, a table of the mock false positive rate among different population pairs; this is a measure of genetic distance between them:

For the Greek sample, the closest populations are Yugoslavs (YU, 0.047), Italians (IT2, 0.0049; IT1, 0.053), and Austrians (AT, 0.054). Most distant ones are Finns (FI, 0.142), Germans (DE1, 0.117), Dutch (NL, 0.112), 英国 (英国, 0.106), and Norwegians (NO, 0.103). This parallels the observation in [6] that in the first two principal components, Greeks are closest to Yugoslavs and Italians among the studied groups.

Auton et al. [9] studied a sample of Greeks from Greece and Cyprus in a global context of 3,845 individuals based on about 450K SNPs. The results of the STRUCTURE analysis are shown below, with increasing number of clusters starting from K=2 (top row). The studied individuals from Greece (#15) 和塞浦路斯 (#9) appear unremarkable in this analysis. It is evident that, in comparison to worldwide populations, the studied Europeans are fairly homogeneous, composed primarily of the “红” component, with no apparent significant contributions from ancestral elements typical of other continental groups.

1. 大号. Luca Cavalli-Sforza, “Genes, peoples, and languages,” Proc. Natl. Acad. Sci. 美国, 卷. 94, pp. 7719-7724, 7 月 1997.
2. Qasim Ayub et al., “Reconstruction of Human Evolutionary Tree Using Polymorphic Autosomal Microsatellites,” American Journal of Physical Anthropology, 122:259–268 (2003)
3. Marc Bauchet et al., Measuring European Population Stratification using Microarray Genotype Data, American Journal of Human Genetics (in press), (2007)
4. Price AL, Butler J, Patterson N, Capelli C, Pascali VL, et al. (2008) Discerning the Ancestry of European Americans in Genetic Association Studies. PLoS Genet 4(1): e236. doi:10.1371/journal.pgen.0030236
5. Tian C, Plenge RM, Ransom M, Lee A, Villoslada P, et al. (2008) Analysis and Application of European Genetic Substructure Using 300 K SNP Information. PLoS Genet 4(1): e4. doi:10.1371/journal.pgen.0040004
6. Lao O. et al. (2008) Correlation between Genetic and Geographic Structure in Europe, Current Biology doi:10.1016/j.cub.2008.07.049
7. Novembre J. et al. (2008) Genes mirror geography within Europe, Nature doi:10.1038/nature07331
8. Tehva Lu T. et al. (2009) An evaluation of the genetic-matched pair study design using genome-wide SNP data from the European population, Eur J Hum Genet doi:10.1038/ejhg.2008.266
9. Auton A. et al. (2009) Global distribution of genomic diversity underscores rich complex history of continental human populations, Genome Research, doi:10.1101/gr.088898.108

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