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。     

龙脑香科植物望天树的居群遗传结构及分化

运用“水平切片淀粉凝胶是泳等分析”方法,对国家一级珍稀濒危保护植物望天树（Parashorea chinensis)进行了遗传多样性和居群分化的研究,通过对分布于滇南,滇东南和桂西南的9个天然居群（中国科学院西双版纳热带植物园引种载培的2个人工居群作为对照）,11个酶系统16个等位酶位点的研究表明,望天树群体内遗传变异水平极低,多态位点比率P为6．25％－12．50％（平均为6．82％）,等位基因平均数A为1．06－1．13（平均为1．07）,平均期望杂合度He为0．032－0．054（平均为0．035）,平均观测杂合度Ho为0．063,所有居群Pgm-1位点的基因型均为杂合体,其余位点的基因型均为纯合体,居群间存在低水平的遗传分化,GST值为0．030,结果表明不同于其它热带植物的报道,望天树群体的遗传结构单一,一方面反映了群体内存在大量的内繁育（无融合生殖,近交）,另一方面也说明了在进化过程中该种曾经历了严重的瓶颈效应,遗传变异大量丧失。     

新疆维吾尔族四个STR位点遗传多态性分析

研究新疆维吾尔族人群D16S539、D13S317、D7S820和D5S818的STR基因位点的基因及基因型分布,获得4个基因座的群体遗传学数据。采用PCR扩增技术和基因扫描技术进行样本STR遗传结构分析,并与其他种族、人群的等位基因频率进行比较。结果表明4个基因位点在新疆维吾尔族人群中均具有遗传多态性。4个基因座的基因型分布均符合Hardy-Weinberg平衡定律（P＞0.05）,不同人群基因频率分布存在一定的差异,所得到的等位基因频率等数据可为遗传学研究、法医个体畜产品识别及亲子鉴定提供依据。     

山西猪种及其杂种群体H-FABP基因的PCR-RFLP研究

利用PCR－RFLP技术对马身猪、山西白猪及其杂种群体共286头猪的心脏脂肪酸结合蛋白（H-FABP）基因5′－上游区（HinfⅠ-RFLP）和第二内含子内（HinfⅠ*-RFLP和Hae Ⅲ-RFLP）的遗传变异进行了研究。结果表明：（1）在Hae Ⅲ-RFLP位点上,马身猪均为DD纯合子,而其他猪群在此位点上均存在变异,马身猪的杂种群体在该位点上只有两种基因型（DD、Dd）;（2）在5′－上游区的HinfⅠ-RFLP位点上,杜洛克猪×山西白猪的杂种群体只有HH基因型,而其他群体都表现出多态性,马身猪等位基因h的频率为0.9727;（3）在第二内含子内的HinfⅠ*-RFLP位点上,马身猪表现出两种基因型（BB、Bb）,等位基因B的频率为0.9667;（4）在HinfⅠ*-RFLP和Hae Ⅲ-RFLP位点上,所有猪群均处于Hardy –Weinberg 平衡状态。     

水稻籼粳交DH群体籽粒充实度的遗传分析

籽粒充实度差是限制亚种间杂交稻产量潜力发挥的重要因素。作者对籼粳交（圭630／02428）DH群体的籽粒充实度进行了研究,结果表明,籽粒充实度是受多基因控制的数量性状,在该DH群体中发生分离的基因估计数为5－6对。通过估测三级（偏度）和四级（峰度）统计量,检测到控制籽粒充实度的多基因间存在重叠作用。DH群体中籽粒充实度表现出明显的超亲分离,表明基因重组可实现控制籽粒充实度的增效基因的聚合。籽粒充实度与单穗产量、穗均实粒数和干物质／总库容之比呈显著或极显著正相关,与千粒重、穗均颖花数和穗均总库容相关不显著。     

欧洲刺槐种源群体遗传结构和多样性

对来自欧洲和美国的 18个刺槐种源子代进行了等位酶分析。可进行遗传分析的 7个酶系统 (Amy,Fe,L ap,Idh,Mdh,6 Pgd,Skd)中有 14个基因位点 ,其中 12个位点具有多态性。每个多态位点平均等位基因数 (A/L )变化在 1.5 6～ 3.6 7之间 ,平均基因型数 (G/L)变化在 1.6 1～ 7.11之间 ,平均等位基因有效数目 (Ae)变化在 1.0 2～ 2 .5 0之间 ,预期杂合度 (H e)变化在0 .0 2～ 0 .5 6之间。不同种源群体之间也存在较大的遗传差异 ,在 8个德国种源中 ,各群体的 A、Ae、和 H e等相对较小 ,但不同群体间差异较大。各位点等位基因频率在不同种源群体间变化也较大 ,表明德国各种源群体内遗传变异相对较小 ,但群体间差异较大。来自匈牙利和斯洛伐克的 8个种源群则相反 ,各群体的 A、Ae、和 H e等相对较大 ,而不同种源群体间差异则较小 ,各位点等位基因频率在种源群体间变化相对一致 ,表明这两个国家的种源群体内变异较大 ,但不同种源群体间差异较小。欧洲的刺槐种源并未形成明显的地理变异模式 ,而且欧洲的种源和来自原产地的美国种源相比 ,没有发现明显的差异。经过 Hardy-Weinberg平衡检测证明 ,88.4 1%位点符合 H- W遗传平衡 ,表明各群体基因频率和基因型频率保持较高的稳定性 ,且种源内的变异大于种源间变异 ,94 .     

鸡Myostatin基因单核苷酸多态性的群体遗传学分析

肌肉生长抑制素是控制骨骼肌生长发育的重要细胞因子,采用PCR－SSCP和测序的方法发现了5个位于Myostatin基因5′－和3′－调控区的单核苷酸多态性位点,对北京油鸡、白耳鸡、石歧杂、矮小黄鸡、小型黄鸡、惠阳胡须鸡、隐性白羽鸡、海兰、AA鸡等不同鸡种的该单核苷酸多态性分析结果表明：Myostatin基因的5′调控区引物P60／P61扩增片段多态性是由3个核苷酸的改变而产生的[分别是G→A（304位）、A→G（322位）、G→（344位）],引物P93／P94扩增片段的多态性是由G→A（167位）突变造成的,引物P117。P118PC扩增片段多态性是由T→C（177位）造成的。3′调控我引物P80／P81扩增片段多态性是由第7263位A突变为T造成的,引物P76／P77扩增片段多态性是由A→G（6935位）造成的。不同鸡种群体遗传学分析表明,5′－调控区引物60／P61扩增片段多态性片段多态性是由A→G（6935位）造成的。不同鸡种群体遗传学分析表明,5′－调控区引物P60／P61扩增片段多态性位点在北京油鸡的基因型频率分布与其他的品种有很大的差异,其BB型频率为0．700,AA基因型频率仅为0．033,而其他鸡种中以A基因优势;对于引物P93／P94,品种间的基因型频率差异极显著（P＜0．01）,北京油鸡和AA鸡的EE型频率鸡种中以A基因占优势;对于引物P93／P94,品种间的基因型频率差异极显著（P＜0．01）,北京油鸡和AA鸡的EE型频率低于其他品种,白耳鸡和海兰蛋鸡以EE型为主,其频率高于其他品种;3′－调控区引物P80／P81多态怀位点在9个鸡种中都是等位基因C占优势。引物P76／P77,总体上MM型的频率较低,杂合子MN型的频率较高。     

贵州从江侗族威宁彝族、荔波瑶族谷胱甘肽S-转移酶M l、Tl 和Pl 的基因多态性研究

目的：研究贵州从江侗族、威宁彝族、荔波瑶族的GSTs基因多态性。方法：在隔离自然人群中,采用多重等住基因特异聚合酶链反应方法分析GSTM1和GSTT1基因多态性,同时采用PCR-RFLP的方法和TaqMan-MGB探针基因分型方法分析GSTP1（A1578G）基因多态性。结果：贵州从江侗族、成宁彝族、荔波瑶族的GSTM1和GSTT1纯合缺失基因型频率分别为59．6％～71．2％、39．4％～72.5％。其GSTP1（A1578G）基因型频率分别为：野生型（AA）为63.3％～75％、杂合子（AG）为23.2％～35．8％、纯合突变型（GG）为0～1.9％。等位基因频率：A为81．2％～86．6％,G为13．4％～18.8％。结论：贵州从江侗族、威宁彝族、荔波瑶族的GSTM1纯合缺失基因型频率在民族间差异无统计学意义,GSTP1（A1578G）基因型频率和等住基因频率在民族间差异无统计学意义,且其等位基因频率均符合Hardy-Weinberg平衡,但其GSTT1纯合缺失基因型频率在民族间差异有统计学意义（P〈0．05）。     

基于InDel标记分析305份中国甘薯登记品种遗传多样性

对甘薯育成品种进行亲缘关系评价,是了解其遗传背景并有效利用种质资源的重要前提。利用本课题组前期开发的23对InDel引物对305份中国甘薯登记品种进行基因型分析,共扩增出56个条带,其中53个条带具有多态性,多态率达94.6%。多态信息量（PIC）、Nei′s遗传多样性指数（H）、观测杂合度（Ho）和期望杂合度（He）的平均值分别为0.4098、0.4451、0.6003、0.4460。群体结构分析表明,群体数在K=2时ΔK达到最大值,K=4时有个小高峰;北方薯区和长江流域薯区在2个组群内均匀分布,南方薯区大部分（72.97%）汇聚在组群2。主坐标分析（PCoA）中南方薯区有部分汇聚,整体没有划分出明显的簇群。聚类结果将群体划分为4个主要类群,北方薯区和长江流域薯区的品种在类群Ⅰ、Ⅱ、Ⅲ和Ⅳ中均匀分布,南方薯区主要（77.03%）集中于类群IV,这一聚类结果与群体结构研究、主坐标分析基本一致。通过系谱分析筛选出登记品种的13个主要亲本材料,各育种单位存在重复利用亲本进行正反交培育的情况。本研究将分子标记结果与系谱信息相结合,初步表明中国甘薯登记品种的亲缘关系较近,遗传背景狭窄,为甘薯的...     

A fundamental relationship between genotype frequencies and fitnesses

The set of possible postselection genotype frequencies in an infinite, randomly mating population is found. Geometric mean heterozygote frequency divided by geometric mean homozygote frequency equals two times the geometric mean heterozygote fitness divided by geometric mean homozygote fitness. The ratio of genotype frequencies provides a measure of genetic variation that is independent of allele frequencies. When this ratio does not equal two, either selection or population structure is present. Within-population HapMap data show population-specific patterns, while pooled data show an excess of homozygotes.     

最大信息熵原理与群体遗传平衡

建立了用最大信息熵原理推导群体遗传平衡定律的统一数学模型,并给出了模型的统一解,此解正是Hardy-Weinberg定律所给出的平衡群体的基因型频率,说明当群体信息熵达到最大时,群体基因型频率不再变化,即达到“平衡”。这证明了最大熵分布就是Hardy-Weinberg平衡分布。Hardy-Weinberg平衡定律与最大信息熵原理的内在一致性说明,杂交和随机交配是一个不可逆过程,使群体基因型信息熵增大,无序性增,是选择和近亲交配使群体的信息熵降低,有序性增加,育种过程实际就是调节群体信息熵的过程。过程信息熵的含义是表示一个概率分布的不确定性,最大熵原理意味着在一定的约束条件,选择具有最大不确定性的分布,从而其分布是最为随机的。最大熵原理在信息,工程,天文,地理,图像处理,模式识别等自然科学和社会科学领域都有广泛的成功应用,本文从群体遗传学角度证明了这一原理具有普遍适用性。熵是描述系统状态的函数,而最大熵原理则表明了系统发展变化的趋势,系统的最终状态必然是熵增加至最大值的状态,对于任何系统都是如此。因此,群体遗传系统的平衡定律可以统一用最大熵原理进行判定和描述;任意群体的基因型信息熵在随机交配世代传递时有不断增加的趋势;在一定约束条件下基因型信息熵达到最大值时,就称之为达到遗传平衡。本文将信息论原理应用于群体遗传学研究,揭示了基因信息熵的生物学意义,并表明可以用信息学和控制论的原理和方法来研究群体遗传学问题。     

Major histocompatibility complex (MHC) heterozygote superiority to natural multi-parasite infections in the water vole (Arvicola terrestris)

The fundamental role of the major histocompatibility complex (MHC) in immune recognition has led to a general consensus that the characteristically high levels of functional polymorphism at MHC genes is maintained by balancing selection operating through host–parasite coevolution. However, the actual mechanism by which selection operates is unclear. Two hypotheses have been proposed: overdominance (or heterozygote superiority) and negative frequency-dependent selection. Evidence for these hypotheses was evaluated by examining MHC–parasite relationships in an island population of water voles (Arvicola terrestris). Generalized linear mixed models were used to examine whether individual variation at an MHC class II DRB locus explained variation in the individual burdens of five different parasites. MHC genotype explained a significant amount of variation in the burden of gamasid mites, fleas (Megabothris walkeri) and nymphs of sheep ticks (Ixodes ricinus). Additionally, MHC heterozygotes were simultaneously co-infected by fewer parasite types than homozygotes. In each case where an MHC-dependent effect on parasite burden was resolved, the heterozygote genotype was associated with fewer parasites, and the heterozygote outperformed each homozygote in two of three cases, suggesting an overall superiority against parasitism for MHC heterozygote genotypes. This is the first demonstration of MHC heterozygote superiority against multiple parasites in a natural population, a mechanism that could help maintain high levels of functional MHC genetic diversity in natural populations.     

Genetic Variation in a Heterogeneous Environment. II. Temporal Heterogeneity and Directional Selection

The maintenance of genetic variation is investigated in a finite population where selection at an autosomal locus with two alleles varies temporally between two environments and the heterozygote has an intermediate fitness value. When there is additive gene action and equal selection in both environments, the autocorrelation between subsequent environments must be negative for more maintenance of genetic variation than for neutrality. The maximum maintenance occurs when there is equal selection in the two environments and the autocorrelation approaches ^-1.0 (for a stochastic model), or when there is short repeating cycle such as one related to seasons. Also comparison of the effects of stochastic variation in selection in finite and infinite populations is made by using Monte Carlo simulation. One situation was found where temporal environmental variation maintains genetic variation very effectively even in a small population and that is when there is evolution of dominance, i.e., the heterozygote is closer in fitness to the favored homozygote than the other homozygote. An important conclusion is that in a finite population genetic tracing of environmental change, particularly when there is a positive autocorrelation between environments or a long environmental cycle, leads to an increased loss of genetic variation making such a response undesirable in the long term, a result different from that in infinite populations.     

Effects of the PPARG P12A and C161T gene variants on serum lipids in coronary heart disease patients with and without Type 2 diabetes

We investigated whether PPAR-γ2 gene polymorphisms are associated with serum lipids and the occurrence of coronary heart disease (CHD) prospectively characterised for the presence or absence of Type 2 diabetes in a Turkish population. Our study included 202 patients with CHD (102 with diabetes, 100 without diabetes) and 105 controls. PPARγ genotypes were determined by PCR-RFLP technique. The PPARγ-C161T CC homozygote genotype was associated with significantly increased CHD risk when compared with the T allele carriers (CT+TT) in CHD patients with diabetes (OR:1.951, 95%CI: 1.115-3.415, P = 0.019), whereas PPARγ-P12A polymorphism was not associated with CHD risk (P > 0.05). Serum HDL-C levels were significantly lower in controls with the P12A heterozygote when compared with the P12P homozygote (P = 0.002). In the CHD patients with diabetes, CT heterozygote genotype showed higher serum triglyceride than the CC homozygote genotype (CT:2.42 ± 1.89 vs. CC:1.61 ± 0.21, P = 0.015). Our findings shows the association of these two polymorphisms with serum triglyceride levels, which was increased in the order of P12P-CC < P12P-CT < P12A-CC < P12A-CT in the CHD patients with diabetes. Furthermore, we observed that the increasing effects of the CT genotype on serum triglyceride levels could be modified by PPARγ P12A polymorphism (P12A-CT:2.30 ± 1.75 vs. P12P-CC:1.79 ± 1.14, P = 0.028). We suggested that homozygote CC genotype of the PPARγ C161T polymorphism might be associated with an increased CHD risk especially in patients with diabetes. We observed that the C161T CT heterozygote genotype shows an unfavorable effect on serum lipid profile in CHD patients with diabetes and this effect was weaken with the presence of P12P homozygote genotype.     

Plasma resistin, associated with single nucleotide polymorphism -420, is correlated with C-reactive protein in Chinese Han patients with spontaneous basal ganglia hemorrhage

We examined a possible relationship -420C>G SNP of the resistin gene with plasma resistin and C-reactive protein concentrations in intracerebral hemorrhage. Three hundred and forty-four Chinese Han patients with intracerebral hemorrhage and 344 age- and gender-matched healthy controls were included in our study. Plasma resistin and C-reactive concentrations were measured and SNP -420C>G was genotyped. The genotype frequencies in controls and patients were not significantly different (P = 0.672). Plasma resistin and C-reactive protein levels were significantly different between the SNP -420C>G genotypes, even after adjustment for age, gender and body mass index. The common homozygote (C-C) had the lowest resistin and C-reactive protein plasma concentrations; the plasma resistin and C-reactive protein concentrations in the heterozygote (C-G) and the rare allele homozygote (G-G) did not differ significantly. Plasma resistin levels were significantly associated with plasma C-reactive protein level. We conclude that SNP -420C>G of the resistin gene could be involved in the inflammatory component of intracerebral hemorrhage through enhanced production of resistin.     

Genetic and phenotypic polymorphisms of the A subunit of Coagulation factor XIII in Japanese population

To clarify whether genetic polymorphisms in exon 14 of Coagulation factor XIII A-subunit gene (FXIIIA) affect phenotype expressions, we studied genetic polymorphisms in exon 14 of FXIIIA in a Japanese population and the relationship between the genetic polymorphisms and phenotype expression. Genetic polymorphisms in exon 14 of FXIIIA of 144 unrelated Japanese were analyzed by single-strand conformation polymorphism. Plasma FXIIIA antigen concentrations, FXIII activities, and phenotype were also determined by two-dimensional electrophoresis. The frequencies of the three genotypes, the homozygote (AD), the homozygote (BC) and the heterozygote (AD/BC), were 77.1, 0.7, and 22.2%, respectively. The gene frequencies of AD and BC were 0.88 and 0.12. We detected AD (GTT x GAG) and BC (ATT x CAG) at codon 650 and 651 of exon 14. There were no significant differences of FXIIIA antigen concentrations and FXIII activities between these genotypes. We detected three pl differences among them as being pls of 5.3, 5.6, 5.8 in the homozygote (AD) and the heterozygote (AD/BC), and a pl of 5.8 in the homozygote (BC). These polymorphisms affected isoelectric mobility, but did not affect protein levels, enzyme activities, or the molecular weight of FXIII.