Below are excerpts from the study “Genetic Relationships among Japanese, Northern Han, Hui, Uygur, Kazakh, Greek, Saudi Arabian, and Italian Populations Based on Allelic Frequencies at Four VNTR (D1S80, D4S43, COL2A1, D17S5) and One STR (ACTBP2) Loci.” Human Heredity 48 (1998): pages 126-137. by Yoshihiko Katsuyama, et al.:
“The genetic polymorphism at four variable number of tandem repeats (D1S80, D4S43, COL2A1, D17S5) and one short tandem repeat (ACTBP2) loci was assessed by polymerase chain reaction analysis of genomic DNA obtained from blood samples of eight human populations (Japanese, Northern Han, Hui, Uygur, Kazakh, Saudi Arabian, Greek, Italian). […] A dendrogram constructed by the neighbor-joining method based on the allele frequencies of the five loci suggested that the five Asian populations (Japanese, Northern Han, Hui, Uygur, and Kazakh) formed one cluster, whereas the two European populations and one West Asian population (Italian, Greek, and Saudi Arabian) formed another. The genetic relationship among these populations may have been greatly influenced by admixture as a result of the migration of individuals along the Silk Road throughout history.”
Many ethnic groups now live in Central Asia as a result of migration of their ancestors to this region. In the 17th century, the Mongols led by Genghis Khan conquered the area from China to Eastern Europe. Moreover, many ethnic migrations took place along the Silk Road, leading to the settlement of East Asia, including the islands of Japan.
The D17S5 VNTR polymorphism located on human chromosome 17  is characterized by a 70-bp core repeat. A total of 14 alleles was observed in the eight human populations studied (table 3). The distribution patterns for alleles 1 and 2 among the eight populations differed markedly. Allele 1 was more frequent in the Japanese, Northern Han, and Hui populations than in the Kazakh, Uygur, Greek, and Italian populations.
The dendrogram shown in figure 1 was constructed by the neighbor-joining method on the basis of the allele frequencies of the four VNTR loci and the single STR locus examined in this study. The Japanese, Northern Han, Uygur, and Kazakh populations formed a single cluster, and the Italian, Greek, and Saudi Arabian populations formed another.
Fig. 1. Dendrogram constructed by the neighbor-joining method showing the relationships among eight human populations based on allele frequencies of five loci. Bootstrap probabilities of 2,000 resamplings of five loci are shown on internal branches.Source
Two previous studies of genetic distance for various human populations were based on genetic markers associated with human leukocyte antigen (HLA) and immunoglobulins (Gm) loci [19, 31]. Imanishi et al.  constructed a dendrogram based on the allele frequencies of two serologically typed HLA-A and HLA-B class I loci of 77 ethnic groups. The 77 populations were classified into four distinct groups (African, Oceanian, Asian, and Caucasoid), and populationslocated on the boundaries of these four groups were located on the borders between groups on the phylogenetic tree. The analysis revealed that several populations in central Asia, including the Ukrainian, Kazakh, and Uygur populations, were on the border between the Caucasoid and Asian groups, whereas the Japanese, Korean, and Tibetan populations were positioned on the border between the Asian and Oceanian groups.
Matsumoto  showed that Mongoloid populations were characterized by four Gm haplotypes (Gm ag, Gm axg, Gm ab3st, and Gm afb1b3) and could be divided into two groups: A northern group characterized by high frequencies of the haplotypes Gm ag and Gm ab3st and a low frequency of Gm afb1b3, and a southern group characterized by a high frequency of Gm afb1b3 and low frequencies of Gm ag and Gm ab3st. The Japanese and Northern Han belong to the northern group on the basis of these criteria. In contrast, the Hui and Uygur populations showed five Gm haplotypes: Gm fb1b3, characteristic of Caucasoids, in addition to the four Gm haplotypes observed in Mongoloids. The Uygur population was characterized by a high prevalence of the Caucasoid haplotype Gm fb1b3, whereas the Hui population showed a higher frequency of the Mongoloid haplotype Gm afb1b3. As suggested by Matsumoto , the actual genetic distances shown in table 8 also support the fact that the Hui population is basically Asian with some European admixture (Hui vs. Northern Han and Italian: 0.130 and 0.175), while the Uygur population is basically European with some Asian admixture (Uygur vs. Northern Han and Italian: 0.150 and 0.149).
Our analysis of five VNTR or STR loci has shed light on the genetic relationships among eight groups and supports the results of the HLA and Gm studies [19, 31]. The allelic distributions of these five loci in the Hui population were relatively similar to those in the Japanese and Northern Han, whereas the allelic distribution patterns for the Kazakh and Uygur populations appeared intermediate between those for Northern Han and Italian populations. These results suggest a strong genetic link between the Japanese and Northern Han.
A dendrogram constructed by the neighbor-joining method based on the allele frequencies of the five loci revealed that five Asian populations (Japanese, Northern Han, Hui, Uygur, and Kazakh) formed one cluster, whereas the two European populations and one West Asian population (Italian, Greek, and Saudi Arabian) formed another at a genetic distance of 0.068. The geographically neighboring populations were closely related according to this approach. These genetic relationships among these neighboring populations may have been substantially influenced as a result of admixture through migration along the Silk Road. Our phylogenetic tree analysis also demonstrated the close racial relationship between the Japanese and Northern Han. Source
The main result of another study “Population origins in Mongolia: genetic structure analysis of ancient and modern DNA.” was that there was genetic similarity observed among Mongolian samples from different periods and geographic areas. Many Mongols live in the independent country of Mongolia. Others live in the Inner Mongolia region of north-central China. There are also Mongols in parts of Russia. There are two main divisions of the Mongol people: eastern Mongols (Khalkha Mongols who are the most numerous, Inner Mongolians, and Buryats) and Oirats. Yet another study showed these northern populations arrived there more than 30,000 years ago before the Last Glacial Maximum (LFM) (corroborated by Siberia’s extensive Upper Palaeolithic archaeological record), and before the expansion of other later populations from the south, post-LGM around 15,000 years ago.
One such expansion involved Buryat people to Japan. Scientists have determined that the Jomon (and Ryukyuan and Ainu) people carry a genetic marker called the ab3st haplotype or blood marker that is shared by Mongoloid populations, found today among the Korean, Tibetan, Tungus, Eskimo and Yakut peoples, and that marker is commonest among the Buryat people living around Lake Baikal. The Gm ab3st gene, which is found with its the highest incidence among the northern Baikal Buriats, flows in all directions. However, this gene shows a precipitous drop from mainland China to Taiwan and Southeast Asia and from North to South America, although it is still found in high frequency among Eskimos, Koryaks, Yakuts, Tibetans, Olunchuns, Tungus, Koreans, Japanese, and Ainus. From the study “Characteristics of Mongoloid and neighboring populations based on the genetic markers of human immunoglobulins” we can gather that the earliest or one of the earliest arrivals of humans to settle Japan belonged to northern Mongoloids, originating in Siberia, most likely in the Baikal area of the Soviet Union.
Furthermore, scientists have recently extracted the mitochondrial DNA extracted from some human bones (some of the oldest) about 2,500 years ago from the Jomon era. Their recent research showed the mitochondrial DNA of 30 Jomon bodies was close to that of the Buryat population of southern Siberia, while DNA of only three bodies was close to that of the Korean, Chinese and Taiwanese populations. This particular mitochondrial DNA pattern can also be found today in many other Japanese women, at a ratio of one out of 10 women.
Experts have followed the trail of this mitochondrial DNA pattern even further back in time, and deep into Tibetan borders and Siberia. Experts now conclude that the prehistoric Japanese people and ancestors of the Jomon people originated from somewhere around Lake Baikal area in Russia (currently called Buryatia which is known to have been inhabited as long ago as 23,000 years ago).
Back then during the ice ages, only small tribes of paleo-asiatic stone tool using hunters had been able to survive the harsh climate of the glacial ages up to 25,000 years by living in warm pockets along Lake Baikal and other bodies of water in Siberia, India, China, as well as in the Altai mountains. When the global climate started to warm up some of these hunters started moving south in pursuit of large animals such as mammoths, and further to Japan (while others may have crossed the Bering strait to reach the North American continent). Scientists identify these Buryat tribes from the Baikal area who migrated into Southeast Asia, southwards into the Korean peninsula and into Eurasia, the Mongoloid tribes.
Christine Keyser-Tracqui, Eric Crubézy, Horolma Pamzsav, Tibor Varga, and Bertrand Ludes. “Population origins in Mongolia: genetic structure analysis of ancient and modern DNA.” American Journal of Physical Anthropology 131:2 (October 2006): pages 272-281.