Polymorphisms at locus D1S80 and other hypervariable regions in the analysis of Eastern European ethnic group relationships

Background: It has been hypothesized that, whereas many loci are used to generate phylogenetic relationships, the utilization of those that yield the most information could increase the accuracy of any multilocus phylogenetic reconstruction. Among these is the D1S80 hypervariable minisatellite region, which has been shown to be highly polymorphic globally, and it was of interest to compare the nearest neighbours and distant populations of Eastern Europe using the D1S80 polymorphism.

Aim: The study evaluated the capacity of the D1S80 locus to discriminate between populations from different ethnic groups in Russia and the Republic of Belarus, revealing the polymorphism parameters of the populations studied.

Subjects and methods: Hypervariable D1S80 minisatellite polymorphism was studied in 15 populations, belonging to six distinct ethnic groups from the Russian Federation (Russians, Komis, Maris, Udmurts, Kalmyks, and Yakuts) and the Republic of Belarus (Byelorussians). The data were analysed with other results reported for D1S80 polymorphism among Eastern Europeans, and were analysed together with those previously reported for Eastern European populations for the 3′ApoB, DMPK, DRPLA, and SCA1 hypervariable loci. Genetic diversity analysis was carried out using multidimensional scaling (MDS) of Nei's genetic distances.

Results: The Eastern Slavonic populations (Russians, Ukrainians, and Byelorussians) are closely associated, and outermost from populations of Asian origin (Kalmyks and Yakuts). The populations that inhabit the Volga–Ural region (Udmurt, Komi, Mari, and Bashkir ethnic groups) revealed intermediate characteristics.

Conclusion: The clustering of populations demonstrated here using D1S80 alone coincides with the analysis of five hypervariable region (HVR) loci, and is consistent with linguistic, geographic, and ethnohistorical data. These results are in agreement with most studies of mtDNA, Y-chromosomal, and autosomal DNA diversity in Eastern Europe. The D1S80 locus is convenient for population analyses, and may be used as part of a set of similar markers, which should allow the easy resolution of small differences in population structures.     

Apolipoprotein B 3'-VNTR polymorphism in Eastern European populations

Apolipoprotein B 3' (3' ApoB) minisatellite polymorphism was studied in healthy unrelated individuals from the Russian Federation and the Republic of Belarus, in 10 populations from five ethnic groups: Russians, Byelorussians, Adygeis, Kalmyks and Yakuts. The analysis was carried out using PCR and electrophoresis followed by silver staining. Overall, 25 alleles of the 3' ApoB minisatellite, ranging from 25 to 55 repeats, were detected. Heterozygosity indices were high and varied from 0.73 to 0.84. The distributions of alleles of this minisatellite in the Caucasoid populations (Russians, Byelorussians and Adygeis) had a bimodal character, whereas that for Mongoloid populations (Kalmyks and Yakuts) had a unimodal distribution. Nei's genetic distances between the populations studied and some reference populations of Europe and Asia were estimated. Despite their allele distribution homogeneity, different East Slavonic ethnic groups were clearly resolved by multidimensional analyses. The East Slavonic and Adygei populations revealed a high similarity with European Caucasoids. The Mongoloid populations (Kalmyks and Yakuts) were considerably different from those of the European Caucasoid populations, but were similar to other Asian Mongoloid populations. The results demonstrate the variability of 3' ApoB minisatellite polymorphism not only in distant populations but also, to a certain extent, in genetically relative ones.     

Hypervariable human minisatellite DNA markers: D1S80 locus in population studies

Minisatellite loci are a part of the human genome that play an important role in genomic and population studies. The review describes characteristics of this group of hypervariable tandem repeats and models that explain their high diversity. The use of this kind of markers in population genetics studies is demonstrated by the example of D1S80 minisatellite locus. Particular emphasis was placed on the D1S80 diversity in different populations of Eastern Europe. The data on ethno-specific and highly differentiating properties of this locus are presented.     

Genetic variability at the D1S80 minisatellite: predominance of allele 18 among some indian populations

BACKGROUND: Hypervariable minisatellites are considered as useful genetic markers in population studies because they are highly polymorphic, multiallelic and co-dominant in nature. The D1S80 minisatellite is one of the well studied markers, and has been used for differentiating population groups of various geographic, linguistic, cultural and genetic origins. OBJECTIVE: The present study reports the genetic variation observed at the D1S80 minisatellite among seven anthropologically distinct ethnic groups from Kerala state in south India and is compared with other reported Indian and world populations. SUBJECTS AND METHODS: DNA was isolated from the peripheral blood samples of 282 random, normal and healthy volunteers, PCR amplified and electrophoresed on 4% PAGE followed by silver staining. RESULTS: A total of 22 alleles (14-39 repeats) were detected with high heterozygosity (0.63-0.84) and Polymorphic Information Content (PIC) values (0.63-0.83). Allele 18 was the predominant allele, except in Ezhavas. The comparison of allele frequency data with world populations including other studied Indian ethnic groups has revealed that the majority of Indian populations possessed allele 18 as the predominant allele. In contrast, allele 24 was reported to be the predominant allele worldwide with a few exceptions. CONCLUSIONS: This study at the D1S80 minisatellite on seven ethnic groups will provide useful information for the Indian population genetic database. However, the most important observation was the predominance of allele 18 among the majority of Indian ethnic groups. The reason is not clear yet and thus further studies on Indian ethnic groups from different regions are necessary to find out the importance of allele 18 as the predominant allele in Indian population.     

Geographic contiguity and genetic affinity among five ethnic populations of Manipur,India: further molecular studies based on VNTR and STR loci

BACKGROUND: Apart from traditional markers studied among a few numerically small, geographically defined surveys among Mongoloid populations in northeastern parts of India, very little is known about their genomic diversity at the molecular level. PRIMARY OBJECTIVE: This study seeks to investigate how best the variable number tandem repeat (VNTR) and short tandem repeat (STR) loci together can detect the patterns of the genetic affinity among five geographically contiguous, linguistically and socio-culturally diverse Mongoloid-affiliated populations of Manipur in northeastern regions of India. SUBJECT AND METHODS: Blood samples were collected from unrelated and randomly selected volunteers of five ethnic populations (Meitei, Kuki, Naga, Hmar and Manipuri Muslim) from different parts of the state. Allelic variation in four minisatellite loci (D1S7, D4S139, D5S110 and D17S79) and three STR loci (vWA, FESFPS and F13AO1) was studied. RESULTS: Average heterozygosity values among the five groups for the minisatellite range from 68% to 94%, while the hypervariable three STR loci were between 60% and 88%. In the populations, all the studied loci were highly polymorphic, with almost no departure from Hardy-Weinberg equilibrium. The gene differentiation for the VNTR loci was lower and moderate (G(st) = 0.030) in comparison with microsatellites (G(st) = 0.043). The neighbour-joining method of clustering based on both type of molecular markers reveals a close cluster for the tribal groups of Kuki, Naga and Hmar, while Manipur Muslim stand distinct in both the trees. The clustering pattern obtained from the combined DNA marker loci matches more closely the pattern from STR loci than that obtained from VNTR loci. CONCLUSIONS: The results reinforce that using both VNTR and STR loci in detecting regional genetic affinity among the populations is more effective than using VNTR or STR independently, and also confirm the results obtained from the serological and electrophoretic data. However, the clustering pattern obtained from combined DNA markers is more in conformity with the pattern obtained by STR loci rather than with VNTR loci. Despite linguistic, geographical and cultural barriers, the populations show genetic affinity among the four populations except in the case of the migrant Manipur Muslim group.     

Geographic contiguity and genetic affinity among five ethnic populations of Manipur,India: further molecular studies based on VNTR and STR loci

Background : Apart from traditional markers studied among a few numerically small, geographically defined surveys among Mongoloid populations in northeastern parts of India, very little is known about their genomic diversity at the molecular level. Primary objective : This study seeks to investigate how best the variable number tandem repeat (VNTR) and short tandem repeat (STR) loci together can detect the patterns of the genetic affinity among five geographically contiguous, linguistically and socio-culturally diverse Mongoloid-affiliated populations of Manipur in northeastern regions of India. Subject and methods : Blood samples were collected from unrelated and randomly selected volunteers of five ethnic populations (Meitei, Kuki, Naga, Hmar and Manipuri Muslim) from different parts of the state. Allelic variation in four minisatellite loci (D1S7, D4S139, D5S110 and D17S79) and three STR loci (vWA, FESFPS and F13AO1) was studied. Results : Average heterozygosity values among the five groups for the minisatellite range from 68% to 94%, while the hypervariable three STR loci were between 60% and 88%. In the populations, all the studied loci were highly polymorphic, with almost no departure from Hardy-Weinberg equilibrium. The gene differentiation for the VNTR loci was lower and moderate ( G st = 0.030) in comparison with microsatellites ( G st = 0.043). The neighbour-joining method of clustering based on both type of molecular markers reveals a close cluster for the tribal groups of Kuki, Naga and Hmar, while Manipur Muslim stand distinct in both the trees. The clustering pattern obtained from the combined DNA marker loci matches more closely the pattern from STR loci than that obtained from VNTR loci. Conclusions : The results reinforce that using both VNTR and STR loci in detecting regional genetic affinity among the populations is more effective than using VNTR or STR independently, and also confirm the results obtained from the serological and electrophoretic data. However, the clustering pattern obtained from combined DNA markers is more in conformity with the pattern obtained by STR loci rather than with VNTR loci. Despite linguistic, geographical and cultural barriers, the populations show genetic affinity among the four populations except in the case of the migrant Manipur Muslim group.     

Genetic variability at the D1S80 minisatellite: predominance of allele 18 among some Indian populations

Background: Hypervariable minisatellites are considered as useful genetic markers in population studies because they are highly polymorphic, multiallelic and co-dominant in nature. The D1S80 minisatellite is one of the well studied markers, and has been used for differentiating population groups of various geographic, linguistic, cultural and genetic origins.

Objective: The present study reports the genetic variation observed at the D1S80 minisatellite among seven anthropologically distinct ethnic groups from Kerala state in south India and is compared with other reported Indian and world populations.

Subjects and methods: DNA was isolated from the peripheral blood samples of 282 random, normal and healthy volunteers, PCR amplified and electrophoresed on 4% PAGE followed by silver staining.

Results: A total of 22 alleles (14–39 repeats) were detected with high heterozygosity (0.63–0.84) and Polymorphic Information Content (PIC) values (0.63–0.83). Allele 18 was the predominant allele, except in Ezhavas. The comparison of allele frequency data with world populations including other studied Indian ethnic groups has revealed that the majority of Indian populations possessed allele 18 as the predominant allele. In contrast, allele 24 was reported to be the predominant allele worldwide with a few exceptions.

Conclusions: This study at the D1S80 minisatellite on seven ethnic groups will provide useful information for the Indian population genetic database. However, the most important observation was the predominance of allele 18 among the majority of Indian ethnic groups. The reason is not clear yet and thus further studies on Indian ethnic groups from different regions are necessary to find out the importance of allele 18 as the predominant allele in Indian population.     

Regional differences in the genetic variability of Finno-Ugric speaking Komi populations.

The Komi (Komi-Zyryan) people are one of the most numerous ethnic groups belonging to the Finno-Ugric linguistic community. They occupy an extensive territory in north Russia to the west of the Ural Mountains, in the northeast of the East European Plain. This is an area of long-term interactions between Europeans and North Asians. Genetic variability was evaluated in two geographically distinct populations, the Izhemski and Priluzski Komi. We searched for polymorphisms of the TP53 gene (a 16-bp duplication in intron 3 and three RFLPs: for Bsh1236I at codon 72, for MspI in intron 6, and for BamHI in the 3' flanking region) and for variable number tandem repeat (VNTR) polymorphisms of locus D1S80 and of the 3' untranslated region of the gene for apolipoprotein B (ApoB). Some data from our previous studies of TP53, 3'ApoB, and D1S80 variability were involved in the comparison of Komi with other Eastern European populations. Multidimensional scaling analysis of genetic distances was used for the evaluation of genetic relationships between populations. The results revealed some affinity between Priluzski Komi and Eastern Slavonic populations, and significant segregation of Izhemski Komi from other ethnic groups studied. The unique genetic features of Izhemski Komi may have been determined by their ethnogenesis or the pressure of environmental factors, such as special nutrition and adaptation to extreme climatic conditions.     

Experimentally observed germline mutations at human micro- and minisatellite loci

We have analysed close to 30,000 human germline transmission events at five microsatellite loci (D3S1359, HumTH01, HumvWA, HumTPO and HumFES) and four minisatellite loci (D1S80, ApoB, Col2A1 and D17S30). At these loci the mutation rates are similar at the microsatellite and the minisatellite loci, varying from 0.2 x 10(-3) to < 3.3 x 10(-3) and from 0.5 x 10(-3) to 1.5 x 10(-3), respectively. Interestingly, paternal mutations appeared to be dominant at the microsatellite loci, whilst maternal mutations are dominant at minisatellite loci. Based on our data, no unequivocal support for a strict strand-slippage mutation mechanism (gain or loss of a single repeat) was found, although the vast majority of the mutational events were small gains or losses of one to three repeats, and only few unequivocal large gains or losses were observed.     

Mitochondrial DNA variability in Russians and Ukrainians: Implication to the origin of the Eastern Slavs

In order to investigate the origin of the Eastern Slavs, mitochondrial DNA (mtDNA) sequence variation was examined in Russians and Ukrainians by hypervariable segment I (HVS I) sequencing and restriction analysis of the haplogroup-specific sites. No significant differences were found for Russians and Ukrainians when compared to other Europeans – in fact, they fall within the range of gene diversity seen throughout Europe and exhibit the unimodal pattern of pairwise sequence differences. Moreover, HVS I sequences in the Russians and Ukrainians are similar or identical to those found in eastern and western European populations. Despite the small genetic distances between Europeans, phylogenetic analysis reveals a considerable heterogeneity of Eastern Slavonic populations – they do not cluster together onto a phylogenetic tree. Analysis of distribution of rare HVS I types shared between populations of Eastern Slavs and other West Eurasians has shown that Russians share rare haplotypes mainly with Germans and Finno–Ugric populations. Of these, subhaplogroup H1 sequence types, which are defined by different combinations of nucleotides 16192T, 16294T, 16304C, 16311C and 16320T, are found predominantly in common between Russians and German-speaking populations. The data obtained allow us to conclude that the Slavonic migrations in early Middle Ages from their putative homeland in central Europe to the east of Europe were accompanied mostly by the same mtDNA types characteristic for the pre-Slavonic populations of eastern Europe.     

Mitochondrial DNA Variability in Bosnians and Slovenians

Mitochondrial DNA variability in two Slavonic‐speaking populations of the northwestern Balkan peninsula, Bosnians (N = 144) and Slovenians (N = 104), was studied by hypervariable segments I and II (HVS I and II) sequencing and restriction fragment‐length polymorphism (RFLP) analysis of the mtDNA coding region. The majority of the mtDNA detected in Southern Slavonic populations falls into the common West Eurasian mitochondrial haplogroups (e.g., H, pre‐V, J, T, U, K, I, W, and X). About 2% of the Bosnian mtDNAs encompass East Eurasian and African lineages (e.g., M and L1b, respectively). The distribution of mtDNA subclusters in Bosnians, Slovenians and the neighbouring European populations reveals that the common genetic substratum characteristic for Central and Eastern European populations (such as Germans, Poles, Russians and Finns) penetrates also South European territories as far as the Western Balkans. However, the observed differentiation between Bosnian and Slovenian mtDNAs suggests that at least two different migration waves of the Slavs may have reached the Balkans in the early Middle Ages.     

中国云南怒族群体线粒体DNA D环区SNP遗传多态性研究

目的观察怒族群体线粒体DNA单核苷酸多态性（single nucleotide polymorphism,SNP）的群体遗传特点,为法医学鉴定提供线粒体DNA序列多态性的基础数据,并为研究少数民族起源提供科学依据。方法应用ABI3730型遗传分析仪,PCR产物直接测序法,对87名中国云南怒族无关个体线粒体DNAD环Ⅰ区进行序列分析。结果在mtDNA高变区SNP16028～16362之间与Anderson序列比较,怒族87名无关个体中共检出62个碱基突变SNP位点,突变点492个,59个SNP单倍型。怒族mtDNA两个高变区SNP基因差异度为0.9675,偶合概率为0.0437。结论怒族线粒体DNAD环Ⅰ区SNP具有高度多态性,是对怒族群体的个体识别、亲权鉴定以及民族起源的分子研究有用的遗传标记。     

Genetic structure and affinity among eight ethnic populations of Eastern India: based on 22 polymorphic DNA loci.

The nature and extent of genetic variation at 22 polymorphic DNA loci, belonging to three distinct classes, especially, 12 STR loci (D3S1358, vWA, FGA, D5S818, D13S317, D7S820, D8S1179, D21S11, D18S51, HPRTB, F13B, LPL), four VNTR loci (D1S7, D4S139, D5S110, D17S79), and six coding loci (HLDQA1, LDLR, GYPA, HBGG, D7S8, GC) were investigated among eight population groups of West Bengal and Manipur regions of India. Of these, two groups from West Bengal belong to Caucasoid and six (one in WB and five in Manipur) belong to Mongoloid stock. Both STR and the expressed loci show wide diversity among the eight populations. For example, Manipur Muslims show differences in allele frequency when compared to four other regional populations. Similarly, Garo, one of the Mongoloid populations of West Bengal, differ in allele frequency from their counterparts in the Manipur region. Departure from Hardy-Weinberg expectations was observed at certain loci in a few populations (e.g., D21S1137 in Kayastha and Brahmin, HUM F13B in Meitei). Heterozygosity values were higher for Caucasoid than Mongoloid groups. The overall gene differentiation (GST) for STR loci is higher (5.3%) than for those at the expressed region (4.6%). The clustering pattern of the eight populations differs with respect to different classes of genetic markers used. The dendrograms based on six coding loci (HLDQA1, LDLR, GYPA, HBGG, D7S8, GC) differs from those based on STR and VNTR markers. Caucasoid and Mongoloid groups form different clusters and Manipur Muslims are distinct from others. The clustering pattern corresponded with the spatial and ethnic affiliations of the populations. Using different classes of DNA loci at the coding and noncoding region will help to better understand the influence of population structure variables on the genetic structure of populations.     

Crossover breakpoint mapping identifies a subtelomeric hotspot for male meiotic recombination

Segregation analysis of CEPH and other pedigrees yielded six paternal crossover breakpoints in the approximately 85 kb interval between the minisatellite loci D16S309 (MS205) and D16S83 (EKMDA2) in 16p13.3. Three crossovers were mapped to within the same small (<3 kb) interval, which does not co-localize with any tandem repeat array or expressed sequence. Haplotyping of loci harbouring single nucleotide polymorphism (SNP) markers in this interval confirmed the exchange of flanking markers in the three recombinant individuals. Sequence analysis revealed the presence of recombination-associated motifs and binding sites for the protein translin. Haplotyping of 108 individuals from three European populations at four loci harbouring SNPs showed substantial linkage equilibrium across this interval. Hence molecular and population genetic data are consistent with the presence of an intense male-specific recombination hotspot at this locus.     

浙江畲族和汉族人群六个短串联重复序列位点遗传多态性的研究

目的 了解浙江畲族和汉族人群D3S1358、D16S539、TH01、TPOX、CSFlPO、D7S8206个短串联重复序列(short tandem repeat，STR)位点遗传多态性特征。方法 随机抽取108名浙江景宁畲族和102名浙江汉族无血缘关系个体的静脉血，应用AmpFlSTR Cofiler试剂盒扩增6个STR位点，PCR产物经ABI Prism377序列分析仪电泳后，用基因扫描软件进行分析。结果 畲族和汉族人群6个STR位点均符合Hardy—Weinberg平衡，畲族人群D3S1358、D16S539、TH01、TPOX、CSFlPO、D7S820位点杂合度分别为0．8028，0．9148，0．7522，0．6728，0．9123，0．8338，期望排除率分别为0．4067，0．6057，0．4437，0．3200，0．5250，0．5358，个人识别率分别为0．6690，0．7841，0．6447，0．5382，0．7298，0．7296。累积个人识别率为0．9991，累积期望排除率为0．9805，累积多态信息含量是0．9988。在D3S1358、D16S539、TPOX位点畲族人群与汉族人群之间存在显著差异。结论 浙江畲族人群有其自身的STR等位基因分布特征。所得到的数据可为法医个人识别、亲子鉴定及遗传学研究提供依据。     

Autosomal recessive cataract (CTRCT18) in the Yakut population isolate of Eastern Siberia: a novel founder variant in the FYCO1 gene

Congenital autosomal recessive cataract with unknown genetic etiology is one of the most common Mendelian diseases among the Turkic-speaking Yakut population (Eastern Siberia, Russia). To identify the genetic cause of congenital cataract spread in this population, we performed whole-exome sequencing (Illumina NextSeq 500) in one Yakut family with three affected siblings whose parents had preserved vision. We have revealed the novel homozygous c.1621C>T transition leading to premature stop codon p.(Gln541*) in exon 8 of the FYCO1 gene ({"type":"entrez-nucleotide","attrs":{"text":"NM_024513.4","term_id":"1519312749"}}NM_024513.4). Subsequent screening of c.1621C>T p.(Gln541*) revealed this variant in a homozygous state in 25 out of 29 Yakut families with congenital cataract (86%). Among 424 healthy individuals from seven populations of Eastern Siberia (Russians, Yakuts, Evenks, Evens, Dolgans, Chukchi, and Yukaghirs), the highest carrier frequency of c.1621C>T p.(Gln541*) was found in the Yakut population (7.9%). DNA samples of 25 homozygous for c.1621C>T p.(Gln541*) patients with congenital cataract and 114 unaffected unrelated individuals without this variant were used for a haplotype analysis based on the genotyping of six STR markers (D3S3512, D3S3685, D3S3582, D3S3561, D3S1289, and D3S3698). The structure of the identified haplotypes indicates a common origin for all of the studied mutant chromosomes bearing c.1621C>T p.(Gln541*). The age of the с.1621C>T p.(Gln541*) founder haplotype was estimated to be approximately 260 ± 65 years (10 generations). These findings characterize Eastern Siberia as the region of the world with the most extensive accumulation of the unique variant c.1621C>T p.(Gln541*) in the FYCO1 gene as a result of the founder effect.Subject terms: Visual system, Genetics research, Clinical genetics     

D16S539、D7S820和D13S317位点在新疆哈萨克族中的遗传多态性

目的 了解新疆哈萨克族人群D16S539、D7S820和D13S317 3个STR位点的遗传多态性。方法 应用多重PCR扩增，6％变性聚丙烯酰胺凝胶电泳结合银染技术对102名无关个体及8个家系42人的哈萨克族人群进行调查，并与其他人群进行了比较。结果 3个位点分别检测出8、7、8个等位片段，多态性分布符合Hardy-Wdinberg平衡定律，期望杂合度为：0.9439、0.9356、0.9304，累积多态信息量为0.9905、个体识别为0.9998、非父排除率为0.9572，与其他人群比较差异有显著性（P＜0.05），在家系调查中无一突变发现，均按孟德尔遗传规律传递。结论 3个STR位点的综合检验在法医学应用及群体遗传学中显示了较高的价值。     

Somatic mutations in VNTR-Locus D1S7 in human colorectal carcinomas are associated with microsatellite instability

To elucidate mutation mechanisms in hypervariable VNTR loci, we have studied somatic mutation events with the minisatellite probe MSI (VNTR locus D1S7) in 224 colorectal carcinomas (CRC). The D¹ S7 locus consists of a 9-basepair (bp) repeat unit. The copy number varies from about 100 to 2000, and the germline mutation rate is high. Here we demonstrate a high D1S7 somatic mutation rate in CRC (37/224), higher than indicated earlier by others. We atso demonstrate that the most frequent mutational event by far (n = 34) involves small reductions in VNTR fragment size (median loss 22 repeat units, range 2-1.54), furthermore, in one-half of these cases, this event is biallelic. We wanted to test whether these somatic mutations mirror the same genetic instability as seen by RER (replication error), a phenomenon recently described in tumour DNA from both sporadic and familial cases of CRC. All blood/tumour DNA pairs displaying MS1 mutation (n = 37) as well as 37 randomly selected pairs without MS1 mutation were tested with four tetranucleotide short tandem repeats (STRs, microsatellites). There is a strong association between mutations at the D1S7 locus and the occurrence of new STR alleles (P<0.001). This is the first report of the existence of a minisatellite as a marker for genetic instability/RER in colorectal carcinomas. The findings may also cast light upon the mechanism for somatic mutations in this minisatellite. © 1995 Wiley-Liss, Inc.     

成都汉族群体七个短串联重复序列基因座的遗传多态性和法医学应用研究

目的获得中国成都地区汉族群体DIS2142、DIS3733、D2S1774、D3S2459、D21S1409、D21S1437和D21S2055七个短串联重复序列（shoa tandem repeam，STR）基因座的群体遗传学资料，评价它们在法医鉴定的应用价值。方法用PCR、聚丙烯酰胺凝胶电泳、银染技术，对283名成都汉族无血缘关系的个体及50个家庭样品进行检测。结果DIS2142检出11个等位基因，23种基因型；DIS3733检出8个等位基因，19种基因型；D2S1774检出8个等位基因，15种基因型；D3S2459检出7个等位基因，19种基因型；D21S1409检出6个等位基因，12种基因型；D21S1437检出9个等位基因，26种基因型；D21S2055检出20个等位基因，77种基因型；基因型分布符合Hardy．Weinberg平衡定律；50个家庭样品调查证实上述基因座均符合孟德尔常染色体共显性遗传，未发现突变。结论DIS2142、D1S3733、D2S1774、D3S2459、D21S1409、D21S1437和21S2055基因座具有较好的多态性。基因座间独立性分析，证实上述7个基因座之间不存在连锁关系，可作为法医学亲子鉴定和个人识别的遗传标记。     

De novo mutations and allelic diversity at minisatellite locus D7S22 investigated by allele-specific four-state MVR-PCR analysis

We have studied the allelic diversity and de novo mutations at the hypervariable minisatellite locus D7S22. A four-state minisatellite variant repeat unit mapping by PCR (MVR-PCR) method was developed for this purpose, and a substitution polymorphism close to the repeat array was used to design allele-specific flanking primers to study individual haplotypes in genomic DNA. A total of 150 alleles from different allele size groups and flanking haplotypes were mapped. On average, MVR-codes extending 65 repeats (2.4 kb) into the repeat array were obtained. The interspersion patterns of variant repeats were highly polymorphic. However, subgroups of alleles close in size and with identical flanking haplotype revealed common MVR-code characteristics indicating a close evolutionary relationship. Unlike the situation in many other hypervariable minisatellites, no polarized variability was revealed at this minisatellite locus. Fifty four small families with D7S22 de novo mutations were analysed by MVR-PCR. The sites where the length change occurred were revealed in 22 cases, while in 32 cases the mutation obviously occurred further into the repeat array. In agreement with a non-polar distribution of the allelic variation, there was no evidence for a hypermutable hot spot for mutation within the repeat array. Comparison of MVR-codes in the mutant and progenitor in gain mutations indicated that at least one, possibly four cases, reflected inter- allelic events. Together with evidence from DNA sequencing of alleles of <2 kb, this indicates that as many as half of the gain mutations might be inter-allelic events in D7S22. Based on these results, different factors which might affect the mutation rate are discussed.