群体遗传不平衡条件下的结构基因遗传共适应特性

本研究以柴达木山羊、柴达木绒山羊和辽宁绒山羊三个群体共147只山羊为材料,利用聚丙烯酰胺凝胶电泳（PAGE）技术检测了5种血液蛋白质（酶）基因座的遗传多态性,并进行了结构基因遗传共适应的研究,结果发现：45个基因座组合中有10个基因座组合处于遗传不平衡状态,并且这些遗传不平衡皆单纯由遗传共适应差异造成;除辽宁绒山羊Tf-PA-3组合的遗传不平衡包含非等位基因间的遗传共适应差异外,其他基因座组合的遗传不平衡皆由等位基因间的共适应差异,即单基因座的遗传不平衡造成;LAP-EsD组合的共适应差异在群体间有遗传传递现象。Abstract:With the technology of PAGE,the genetic polymorphism of blood protein and enzyme was investigated,and genetic co-adaptability among structural genes was studied in three goat populations(147 goats) including Chaidamu goat(CS),Chaidamu Cashmere goat(CRS) and Liaoning Cashmere goat(LRS) in Qinghai Province,China.The results were showed that the genetic disequilibrium of 10 locus combinations was found among 45 locus combinations in the three goat populations,and these genetic disequilibria were caused only by the difference of genetic co-adaptability among genes,because there didn′t exist the linkage disequilibrium among non-allelic genes.The genetic disequilibrium including the difference of genetic co-adaptability between non-allelic genes was only found at Tf-PA-3 locus combinations in LRS population,the other ones were all caused by the genetic disequilibrium at a single locus.The difference of genetic co-adaptability of LAP-EsD locus combinations could be messaged among different populations.     

中国野生鹌鹑群体遗传共适应特性研究

随机抽取迁飞滞留季节捕获的野生日本鸣鹑40只、野生普通鹌鹑62只和家鹑40只, 采用蒙特卡罗模拟法检验群体遗传不平衡, 运用微卫星DNA标记对两种野生鹌鹑和家鹑群体的遗传共适应特性进行分析, 在3个鹌鹑群体中证实存在遗传共适应特性; 同时构建中性位点遗传共适应的统计模型, 分析遗传共适应特性在分子水平上的效应, 结果表明: 遗传共适应主导了野生日本鸣鹑、野生普通鹌鹑和家鹑群体的遗传不平衡状态, 分别有16.67%, 9.66%和10.05%的非等位基因组合因遗传共适应的影响处于遗传不平衡或极不平衡状态, 几乎所有检测的位点都存在遗传共适应特性, 其在分子水平上的作用更加显著, 维持着群体中大量的稳定多态现象. 这一结果丰富了群体遗传不平衡的概念和内涵, 为了解除连锁之外, 另一重要因素——遗传共适应对群体遗传不平衡的作用提供了科学的依据; 同时也为阐明我国野生鹌鹑的系统地位以及为评价、保护和利用我国野生鹌鹑这一宝贵遗传资源打下基础.     

湖羊结构基因座遗传共适应性分析

根据多座位电泳法检测的结构基因座上等位基因频率分析湖羊群体的遗传共适应性。结果发现, 在显隐性－显隐性模式中未发现座位间的遗传共适应现象, 显隐性－共显性模式中X-p-Cat组合座位以及共显性－共显性模式中Po-CA、Po-Cat组合座位均存在遗传共适应, 表明在湖羊群体中性结构基因座间存在遗传共适应, 而且起主要的作用, 维持着座位间的遗传平衡或者使座位间处于遗传不平衡状态。     

渐近混合群体的混合连锁不平衡及其遗传连锁推断

在渐近混合模型中,混合现象发生在每一世代,通过对其混合连锁不平衡的理论分析,发现混合连锁不平衡与两个子群体间的基因频率差成正比。基于这一点,构造了一个对重组率严格单调的函数（△ker=△／（p1-p2）,其中△代表连锁不平衡）,进而据此推断标记基因座与疾病基因座的遗传连锁。应用人类基因组上不连锁的标记基因提供的连锁不平衡信息,基于病人组数据构造了一个准似然比统计量。模拟结果显示,此检验可用于精确的基因定位。文章亦讨论了参数对检验的影响。     

人类混血群体连锁不平衡的遗传学模型与基因定位

人类混血群体可以说是混合群体的一种特例．在无选择、无突变、无限随机交配群体的假定前提下,研究了亲本群体的基因频率对混血群体及其衍生后代群体连锁不平衡结构的影响,导出了各群体连锁不平衡值的表达式,建立了一个估计基因间重组率的简便方法;同时, 采用估算分子标记与QTL之间连锁不平衡系数的统计分析方法,分析了人类混血群体及其衍生后代群体QTL检测与估计的关系,建立了该关系的系列理论公式．研究结果表明,本方法不仅适用于人类疾病(包括复杂遗传疾病)基因定位,而且适合于人类正常基因的定位,同时也适用于人类普通多基因性状的QTL分析．     

雄性不交换条件下F2群体进行基因定位的计算方法

本文提出在雄性不交换条件下,在F2群体中进行基因定位的计算方法。     

雌雄连锁基因的性别遗传

一、性别决定的研究概况美国遗传学家摩尔根在性别决定中指出,性染色体在生物界中比较普遍的类型有两种:XY型和ZW型.据此得出的结论是,出生的后代雌雄比值相等,但实际情况并非如此.例如有人做鳄类和人类胎儿的性别调查,均不符合1∶1规律.1976年研究哺乳类性别决定的美国免疫学家瓦赫特尔的H-Y抗原决定性别     

雄性不交换条件下F_2群体进行基因定位的计算方法

本文提出在雄性不交换条件下,在Ｆ２群体中进行基因定位的计算方法．     

家畜近亲繁殖群体连锁不平衡的分析

本文分析了家畜近亲繁殖群体连锁位点基因遗传平衡的实现,推导出了配子型频率及基因型频率通用递推公式．研究证明,近交群体不同于随机交配大群体,其连锁不平衡值d（绝对值）随世代的下降速率不仅取决于重组率,而且也依赖于近交速率．近交越剧烈,则d下降越慢;达平衡态时,近交群体d值并不一定等于0．连锁越紧密,近交越剧烈,则平衡d值越大．最后讨论了研究结果在家畜育种中的应用．     

群体遗传平衡定律的应用

群体遗传平衡定律,即哈迪-魏伯格定律,是群体遗传学一个最基本最重要的定律,这是由英国数学家哈迪(Hardy)和德国医生魏伯格(Weinberg)在1908年先后独立地证明过的：在一个随机交配的大群体,如果没有其他因素(如突变、选择、迁移、漂变)的干扰,总是处于一种平衡状态,即从上一代到下一代基因型     

人类复杂遗传疾病QTL分析方法的理论探讨

利用连锁不平衡理论,人类遗传学家已能把影响人类疾病的质量基因定位在小至1cM区域内,有些基因已被克隆出来。罗泽伟等进一步发展统计分析方法检测及估算分子标记与QTL之间的连锁不平衡系数,从而提出了人类复杂遗传病高解析度基因定位的理论策略。以此为基础,进一步探讨了供试群体在双亲基因频率存在差异时检测QTL和检测QTL互作的方法,给出了有关的理论结果。     

Genetic diversity and multilocus structure in sexual Otiorhynchus alpicola populations (Goleoptera: Gurculionidae)

Otiorhynchus alpicola Boh. (Coleoptera: Curculionidae) is distributed on high mountains of central, southern and south-eastern Europe. On the Balkan peninsula, this species is patchily distributed on mountain peaks at heights over 1800 m. To examine the organization of isoenzyme variation of the ten sexual (diploid) populations, starch gel electrophoresis of enzymes was used. The average heterozygosity over 14 gene loci was 0.11. For diploid O. alpicola, F-statistics were used to assess population heterogeneity and substructuring. The data indicate that, compared with other insects, this high-altitude weevil species is genetically very differentiated (the average F _ST= 0.35). In addition, gene-flow among populations was extremely low (the estimates of N_em from Wright's F _ST and Slatkin private-allele methods were 0.47 and 0.83, respectively). Pairwise linkage disequilibrium (LD) parameters were estimated from zygotic frequencies using Burrows' method. The average rate of significant LD in analysed populations of O. alpicola was about 27%. The pattern of LD over the diploid populations indicates that stochastic factors might be a primary cause of the observed multilocus associations.     

Social heterosis and the maintenance of genetic diversity at the genome level

Social heterosis is when individuals in groups or neighbourhoods receive a mutualistic benefit from across‐individual genetic diversity. Although it can be a viable evolutionary mechanism to maintain allelic diversity at a given locus, its efficacy at maintaining genome‐wide diversity is in question when multiple loci are being simultaneously selected. Therefore, we modelled social heterosis in a population of haploid genomes of two‐ or three‐linked loci. With such linkages, social heterosis decreases gametic diversity, but maintains allelic diversity. Genomes tend to survive as complimentary pairs, with alternate alleles at each locus (e.g. the pair AbC and aBc). The outcomes of selection appear similar to fitness epistasis but are novel in the sense that phenotypic interactions occur across rather than within individuals. The model’s results strongly suggest that strong linkage across gene loci actually increases the probability that social heterosis maintains significant genetic diversity at the level of the genome.     

Study on genetic coadaptability of wild quail populations in China

Genetic coadaptability of wild Japanese quail, wild Common quail and Domestic quail populations in China was studied using 7 microsatellite DNA markers and Monte Carlo method to test genetic disequilibrium. The molecular effects of genetic coadaptability were analyzed through a new statistical model of neutral site. The results showed that genetic coadaptability dominated the genetic disequilibrium of the three quail populations, and totally 16.67%, 9.66% and 10.05% of non-allelic combinations were in the genetic disequilibrium in wild Japanese quail, wild Common quail and Domestic quail populations, respectively. Genetic coadaptability existed at almost all the tested sites. In the molecular point of view, genetic coadaptability plays an important role of keeping lots of polymorphisms in natural populations. Therefore, it is another key factor to the genetic disequilibrium in the population except for linkage. The results enrich the conceptions and connotations of genetic disequilibrium, and help us know more about genetic coadaptability and its effects, and lay a foundation of evaluation and protection of wild quail genetic resources in China.