中国人群遗传结构分析

本文根据红细胞血型基因频率,用Harpending和Jenkins(1973)方法计算了中国22个人群间的遗传距离,同时在国内首次运用主坐标分析及其排序方法展示了中华民族的遗传结构,反映出中国东西人群与南北人群间的基因流。     

群体融合对遗传方差的影响

探讨了群体融合对遗传方差的影响,无显性时基因型方差对群体中的基因频率为一凸函数,群体融合将导致它的增加,完全显性时,当群体中显性基因的频率时,群体融合导致基因型方差增加;而当时,融合导致基因型方差减小。超显性时,群体融合导致基因型方差增加,对加性方差和显性方差也分别进行了探讨。     

两对等位基因群体熵的性质

研究了两对等位基因群体熵的性质,并对位点多样度D与基因相对信息量多样度S′(G)进行了比较研究．结果表明,在遗传变异的度量上,位点多样度D与基因相对信息量多样度S′(G)具有一致性,且S′(G)还具有信息学内涵．     

马尾松天然群体同工酶遗传变异

６个马尾松天然群体同工酶分析结果表明：马尾松群体具有较丰富的遗传变异,其多态位点百分率（Ｐ）＝７６．２％;等位基因平均数（Ｎａ）＝２．３９;有效等位基因平均数（Ｎｅ）＝１．６２,平均杂合率（Ｈｅ）＝０．２７３。但群体间遗传分化极小,基因分化系数（Ｇ＿（ＳＴ））＝０．０１７２,遗传距离（Ｄ）＝０．０１１±０．００５。总遗传变异中,约２％来自群体间,而约９８％的遗传变异存在于群体内的个体,并且其变异又主要来源于１／３的基因位点。马尾松群体近似于随机交配群体,绝大多数位点处于平衡状况,但也有约１／３的位点并非随机交配,存在不同程度的近交。     

中国石榴栽培群体遗传多样性的荧光AFLP分析

以中国山东、安徽、陕西、河南、云南和新疆6个栽培石榴群体的85个品种类型为试材,利用荧光标记AFLP对中国石榴群体遗传多样性进行了研究。结果表明：8对引物组合在种级水平扩增的多态性位点数范围从135～185个不等,平均为158.25个,多态位点百分比范围为62.5%～86.11%,平均为73.26%,说明中国石榴品种遗传多样性较为丰富;石榴品种种级水平遗传多样性大于群体水平,6个群体的遗传多样性依次为河南群体〉新疆群体〉陕西群体〉安徽群体〉山东群体〉云南群体,并且具有显著性差异;群体间的遗传分化系数GST为0.2018,说明石榴遗传变异主要存在群体内,群体间的遗传变异占总变异的20.18%,根据基因分化系数,测得的基因流Nm为1.9027,说明中国石榴群体间存在适当的基因交流;UPGMA聚类分析结果表明,同一群体的大部分品种都聚在一起,但同时存在部分基因交流。所有遗传参数表明,中国石榴栽培品种遗传多样性较为丰富,其中河南群体遗传多样性显著高于其他群体,在中国石榴品种选育中具有更为广阔的应用前景。     

中国3个地区汉族人群补体C6的遗传多态性研究

运用聚丙烯酰胺凝胶等电聚焦(PAGIF)和免疫吸引技术,研究了3个地区汉族人群的C6多态性。得到的基因频率如下:漳州市——C6*A:0.4634、C6*B:0.5000、C6*R:0.0366(C6*B2:0.0317);成都市——C6*A:0.4975,C6*B:0.4484,C6*R:0.0545(C6*B2:0.0395);哈尔滨市——C6*A:0.4708,C6*B:0.5219,C6*R:0.0073(C6*B2:0.0073)。蒙古人种的C6*A频率一般都低于0.5,高加索人种的C6*A频率一般都高于0.6。黑人则介于两者之间。蒙古人种与高加索人种的另一个区别在于前者的C6*B2频率在0.03到0.07之间,而后者几乎没有C6*B2。     

菜薹种质内不同大小群体问遗传多样性的RAPD鉴定和比较

为了了解菜薹种质内的遗传多样性,确定适宜的更新群体,从一份菜薹地方品种的200株群体中随机抽取10、15、20、25、30、35和．40株组成不同的群体,利用RAPD技术分析各自的多态位点数、计算多态位点百分率、遗传多样性指数和缺失位点数。通过对各参数的比较结果表明,该种质内单株间的遗传差异较大,大于30株的群体能代表200株群体的遗传多样性。在满足其完全随机交配的前提下,可视为更新的有效群体。根据更新时繁种群体应为有效群体2倍的原则,认为不小于60株的群体为菜薹种质更新比较适宜的群体。     

利用微卫星DNA标记研究绒山羊群体遗传多样性

利用7个微卫星标记对4个绒山羊品种共计18个个体的遗传多样性进行了分析和研究。计算了有效等位基因数、遗传杂合度、遗传距离等,分析了群体相关的遗传变异。结果表明,辽宁多绒山羊的有效等位基因数最大,杂合度最高;而辽宁绒山羊的有效等位基因数最小,杂合度最低。奈氏遗传距离表明,库布齐杂种绒山羊和辽宁多绒山羊的亲缘关系最近,而和阿尔巴斯绒山羊的亲缘关系最远。     

人参不同栽培群体遗传关系的RAPD分析

用随机扩增多态ＤＮＡ（ＲＡＰＤ）标记法对４个人参（Ｐａｎａｘ ｇｉｎｓｅｇ Ｃ．Ａ．Ｍｅｙｅｒ）栽培群体中存在较丰富的遗传多样性。分析一路参、三路参、系选品系５９号、北京参等４个人参栽培群体和１个西洋参（Ｐ．ｑｕｉｎｑｕｅｆｏｌｉｕｍ Ｌ．）群体的遗传分化指数值表明,三路参变异量最大（０．４１６９）,一路参降为０．２５６５,边条参系选品系５９号最低为０．１８８１,表明选择方式和选择代数的纯化作用十分     

计算机模拟在群体遗传教学中的应用

计算机模拟在群体遗传教学中的应用黄远樟（北京师范大学生物学系,北京１００８７５）ＴｈｅＡｐｐｌｉｃａｔｉｏｎｏｆＣｏｍｐｕｔｅｒＳｉｍｕｌａｔｉｏｎｉｎＴｅａｃｈｉｎｇＰｏｐｕｌａｔｉｏｎＧｅｎｅｔｉｃｓＨＵＡＮＧＹｕａｎｚｈａｎｇ（Ｄｅｐａｒｔｍｅ...     

长江流域■种群遗传多样性和遗传结构分析

鱼类群体遗传学研究主要集中在经济鱼类或濒危物种,然而一些经济价值较低的物种的遗传结构却甚少关注。因此,研究选择了经济价值较低的■(Hemiculter leucisculus),共计323尾个体分别来自13个长江流域及其附属湖泊的自然群体。通过扩增线粒体DNA Cytb基因序列片段(1100 bp),以探讨■种群遗传结构和遗传多样性。遗传多样性分析呈现出高单倍型多样性和高核苷酸多样性的模式,表明该种群在长江流域较为稳定。另外,基于线粒体细胞色素b基因的系统发育分析,显示■有5个线粒体谱系(谱系A-F)组成。中性检验和核苷酸错配分布分析均显示谱系A、B、E、F曾经历过种群扩张,并且呈现从上游向中游扩张的规律。谱系间较高且显著的遗传分化指数和显著的系统进化关系,均表明谱系A-F之间存在明显的遗传分化,暗示长江流域可能至少存在4个不同线粒体DNA水平上的种。■种群的遗传结构和多样性可能受到了长江流域特定格局的影响。     

Cryptosporidium varanii takes precedence over C. saurophilum

We present biological as well as genetic analysis of Cryptosporidium varanii at the 18S rRNA and actin loci and show that it is genetically identical to C. saurophilum. As C. varanii was described prior to C. saurophilum, it takes precedence over C. saurophilum and therefore C. saurophilum should be considered a junior synonym of C. varanii.     

Microsatellite variability and heterozygote excess in Elymus trachycaulus populations from British Columbia in Canada

Microsatellite markers were used to assess the genetic diversity and population structure in four populations of Elymus trachycaulus from British Columbia and one population of Elymus alaskanus from Northwest Territories. Fourteen microsatellite loci were used in this study. Our results indicated that E. trachycaulus is highly polymorphic, with an average percentage of polymorphic loci of 96.5% over the four populations. Average expected heterozygosity values (H_E or gene diversity) varied from 0.418 to 0.585 with a mean of 0.497. Most of the genetic variation was found within populations (85%) and the differentiation among populations was found to be 15% (F_st = 0.15). Interpopulation genetic distances corresponded well with the geographic distance between the population sites of origin, as well as morphological characteristics. Tests for Hardy–Weinberg equilibrium (HWE) for all loci and all populations revealed that all loci significantly differ from HWE. Subsequent analysis indicated that departure from HWE at some loci was due to an excess of heterozygotes. Possible explanations for heterozygote excess are discussed. The most likely reason for observed heterozygote excess could be due to the polyploidy nature of the species.     

Genetic detection and quantification of Nosema apis and N. ceranae in the honey bee

The incidence of nosemosis has increased in recent years due to an emerging infestation of Nosema ceranae in managed honey bee populations in much of the world. A real-time PCR assay was developed to facilitate detection and quantification of both Nosema apis and N. ceranae in both single bee and pooled samples. The assay is a multiplexed reaction in which both species are detected and quantified in a single reaction. The assay is highly sensitive and can detect single copies of the target sequence. Real-time PCR results were calibrated to spore counts generated by standard microscopy procedures. The assay was used to assess bees from commercial apiaries sampled in November 2008 and March 2009. Bees from each colony were pooled. A large amount of variation among colonies was evident, signifying the need to examine large numbers of colonies. Due to sampling constraints, a subset of colonies (from five apiaries) was sampled in both seasons. In November, N. apis levels were 1212 ± 148 spores/bee and N. ceranae levels were 51,073 ± 31,155 spores/bee. In March, no N. apis was detected, N. ceranae levels were 11,824 ± 6304 spores/bee. Changes in N. ceranae levels were evident among apiaries, some increasing and other decreasing. This demonstrates the need for thorough sampling of apiaries and the need for a rapid test for both detection and quantification of both Nosema spp. This assay provides the opportunity for detailed study of disease resistance, infection kinetics, and improvement of disease management practices for honey bees.     

The coordinate regulation of pharyngeal development in C. elegans by lin-35/Rb, pha-1, and ubc-18

Organ development is a complex process involving the coordination of cell proliferation, differentiation, and morphogenetic events. Using a screen to identify genes that function coordinately with lin-35/Rb during animal development, we have isolated a weak loss-of-function (LOF) mutation in pha-1. lin-35; pha-1 double mutants are defective at an early step in pharyngeal morphogenesis leading to an abnormal pharyngeal architecture. pha-1 is also synthetically lethal with other class B synthetic multivulval (SynMuv) genes including the C. elegans E2F homolog, efl-1. Reporter analyses indicate that pha-1 is broadly expressed during embryonic development and that its functions reside in the cytoplasm. We also provide genetic and phenotypic evidence to support the model that PHA-1, a novel protein, and UBC-18, a ubiquitin-conjugating enzyme that we have previously shown to function with lin-35 during pharyngeal development, act in parallel pathways to regulate the activity of a common cellular target.     

Genetic diversity of the endangered and endemic species Psathyrostachys huashanica natural populations using simple sequence repeats (SSRs) markers

Psathyrostachys huashanica Keng., a species endemic to China, is only distributed in Huashan Mountain in Shaanxi Province. It has been listed as “national first-class protected rare species.” In this study, the microsatellites of barley were used to analyze genetic diversity of P. huashanica populations sampled from three valleys (Huangpu, Xian and Huashan Valleys) in Mt. Huashan. A total of 33 alleles of 11 loci were detected from 266 individuals. The observed average number of alleles (A) is 2.75; the effective number of alleles (Ae) is 1.67. The percentage of polymorphic loci (PPB) is 58.33% in Huangpu Valley, 75% in Xian Valley, 83.33% in Huashan Valley, and the total PPB is 83.33%. About 77.6% of (F_ST = 0.324) genetic diversity was observed within the subpopulations. Genetic differentiation within each subpopulations was higher than that among the subpopulations. Mean genetic distance is 0.17 (range: 0.010–0.401). Correlation analysis detected significant correlation between genetic distance and vertical distance of altitude in Huashan Valley. Differentiation mainly occurred between the higher altitude subpopulations and the lower altitude subpopulations, suggesting that altitude might be the major factor that restricted the gene flow between different altitude subpopulations and resulted in differentiation of subpopulations.     

First report of genetic hybrids between two very divergent Leishmania species: Leishmania infantum and Leishmania major

The genus Leishmania includes many pathogenic species which are genetically very distant. The possibility of genetic exchange between different strains is still an important and debated question. Very few genetic hybrids (i.e., offspring of genetically dissimilar species) have been described in Leishmania. In this study, we report the first example of genetic hybrids occurring between two divergent Leishmania species, Leishmania infantum and Leishmania major. These two species have distinct geographical distributions and are transmitted by different vector species to different mammalian reservoir hosts. These hybrid strains were isolated in Portugal from immunocompromised patients and characterized by molecular and isoenzymatic techniques. These approaches showed that these chimeric strains probably contained the complete genome of both L. major and L. infantum. We believe this is the first report of genetic hybrids between such phylogenetically and epidemiologically distant species of Leishmania. This raises questions about the frequency of such cross-species genetic exchange in natural conditions, modalities of hybrid transmission, their long term maintenance as well as the consequences of these transfers on phenotypes such as drug resistance or pathogenicity.     

Chloroplast microsatellite diversity of Clintonia udensis (Liliaceae) populations in East Asia

Nineteen populations of Clintonia udensis Trautv. & Mey. were examined to quantify genetic diversity and genetic structure by chloroplast DNA microsatellites (cpSSR). Significant cpSSR genetic diversity (PPB = 63.64%) was detected in this species. Tetraploid populations demonstrated approximately the same level of genetic diversity as the diploid ones. A significant differentiation, however, was found between tetraploids and diploids. Most of the sixteen chloroplast haplotypes were limited to a single population. The level of haplotype diversity was high (Hd = 0.915). AMOVA, PCA and Bayesian clustering analysis revealed that there were significant genetic differences among populations. Inter-population genetic distances among population sites correlated significantly with geographic distances. These results indicate that the mixed-mating – breeding system, limited gene flow, environmental stress, and historical factors may be the main factors causing geographical differentiation in the genetic structure of C. udensis.     

Genetic diversity of indigenous rhizobial symbionts of the Lupinus mariae-josephae endemism from alkaline-limed soils within its area of distribution in Eastern Spain

The genomic diversity of a collection of 103 indigenous rhizobia isolates from Lupinus mariae-josephae (Lmj), a recently described Lupinus species endemic to alkaline-limed soils from a restricted habitat in Eastern Spain, was investigated by molecular methods. Isolates were obtained from soils of four geographic locations in the Valencia province that harbored the known Lmj plant populations. Using an M13 RAPD fingerprinting technique, 19 distinct RAPD profiles were identified. Phylogenetic analysis based on 16S rDNA and the housekeeping genes glnII, recA and atpD showed a high diversity of native Bradyrhizobium strains that were able to establish symbiosis with Lmj. All the strains grouped in a clade unrelated to strains of the B. canariense and B. japonicum lineages that establish symbioses with lupines in acid soils of the Mediterranean area. The phylogenetic tree based on concatenated glnII, recA and atpD gene sequences grouped the Lmj isolates in six different operational taxonomic units (OTUs) at the 93% similarity level. These OTUs were not associated to any specific geographical location, and their observed divergence predicted the existence of different Bradyrhizobium genomic species. In contrast, phylogenetic analysis of symbiotic genes based on nodC and nodA gene sequences, defined only two distinct clusters among the Lmj strains. These two Lmj nod gene types were largely distinct from nod genes of bradyrhizobia nodulating other Old World lupine species. The singularity and large diversity of these strains in such a small geographical area makes this an attractive system for studying the evolution and adaptation of the rhizobial symbiont to the plant host.     

Molecular characterization of a truncated antigen (Wb14) of SXP-1 of Wuchereria bancrofti from four endemic regions in India

Wb14 of Wuchereria bancrofti, an orthologue of Brugia malayiSXP-1 and W. bancrofti SXP-1, was amplified from genomic DNA of W. bancrofti microfilaria collected from four distant geographical locations in India viz., Vellore, Bhubaneshwar, Pondicherry and Sevagram. The gene was sub-cloned in a prokaryotic vector pRSET and expressed in Escherichia coli as a truncated protein (∼23 kDa). The nucleotide sequence of the gene is 98% similar to that of WbSXP-1 and is found to be intron-less. However, the analysis and comparison of the derived amino acid sequence with WbSXP-1 showed that Wb14 is truncated at amino acid position 153. The distribution of the two genes in the studied four geographical locations indicated that WbSXP-1 is prevalent only in parasite samples from Sevagram while Wb14 is present in parasites from all the other locations. Only a limited polymorphism was observed in both the genes among the parasites from different geographical locations.