Transposable mating type genes in Saccharomyces cerevisiae.

A functional copy of the alpha mating type gene of Saccharomyces cerevisiae has been cloned by transformation in yeast. Using the Southern Blotting procedure it has been shown that three distinct genetic loci implicated in mating type interconversion (HML, HMR and MAT) contain sequences homologous to the clone fragment. The restriction fragment associated with each locus exhibits a characteristic size which can be correlated with the mating type allele present at that locus. The characteristic size difference between the a and alpha genetic elements made it possible to demonstrate that the homothallic interconversion of mating types in this yeast occurs by DNA rearrangement as proposed in the 'cassette hypothesis'.     

In vivo genome editing restores haemostasis in a mouse model of haemophilia

Editing of the human genome to correct disease-causing mutations is a promising approach for the treatment of genetic disorders. Genome editing improves on simple gene-replacement strategies by effecting in situ correction of a mutant gene, thus restoring normal gene function under the control of endogenous regulatory elements and reducing risks associated with random insertion into the genome. Gene-specific targeting has historically been limited to mouse embryonic stem cells. The development of zinc finger nucleases (ZFNs) has permitted efficient genome editing in transformed and primary cells that were previously thought to be intractable to such genetic manipulation. In vitro, ZFNs have been shown to promote efficient genome editing via homology-directed repair by inducing a site-specific double-strand break (DSB) at a target locus, but it is unclear whether ZFNs can induce DSBs and stimulate genome editing at a clinically meaningful level in vivo. Here we show that ZFNs are able to induce DSBs efficiently when delivered directly to mouse liver and that, when co-delivered with an appropriately designed gene-targeting vector, they can stimulate gene replacement through both homology-directed and homology-independent targeted gene insertion at the ZFN-specified locus. The level of gene targeting achieved was sufficient to correct the prolonged clotting times in a mouse model of haemophilia B, and remained persistent after induced liver regeneration. Thus, ZFN-driven gene correction can be achieved in vivo, raising the possibility of genome editing as a viable strategy for the treatment of genetic disease.     

复杂遗传性状连锁不平衡基因定位的理论基础(英)

复杂遗传疾病基因的定位克隆要求首先获得疾病位点与遗传标记位点间的高分辨率连锁图谱．研究表明,这一目标可通过建立和筛选适当的候选标记位点与目标性状位点间的连锁不平衡的理论分析模型而实现．但这些模型只适用于位点基因型可以通过实验而准确分型的范围．本文报道在不可测基因型复杂遗传疾病的细微定位理论与方法方面所取得的研究成果．     

A closely linked genetic marker for cystic fibrosis

Cystic fibrosis is a recessive genetic disorder, characterized clinically by chronic obstructive lung disease, pancreatic insufficiency and elevated sweat electrolytes; affected individuals rarely live past their early twenties. Cystic fibrosis is also one of the most common genetic diseases in the northern European population. The frequency of carriers of mutant alleles in some populations is estimated to be as high as 1 in 20, carrying a concomitant burden of about one affected child in 1,500 births. Because little is known of the essential biochemical defect caused by the mutant gene, a genetic linkage approach based on arbitrary genetic markers and family studies is indicated to determine the chromosomal location of the cystic fibrosis (CF) gene. We have now obtained evidence for tight linkage between the CF locus and a DNA sequence polymorphism at the met oncogene locus. This evidence, combined with the physical localization data for the met locus presented in the accompanying paper, places the CF locus in the middle third of the long arm of chromosome 7, probably between bands q21 and q31.     

Theoretical strategies for high-resolution mapping of complex genetic disorders in humans

Positional cloning of gene(s) underlying a complex disease trait poses requirement of a highresolution linkage map between the disease locus and genetic marker loci. Recent researches have shown that this may be achieved through appropriately modeling and screening linkage disequilibrium between the candidate marker locus and the major trait locus. However, these models were restricted to the circumstances where genotyping at the disease locus was feasible. The major limitations of pedigree-based linkage analyses were addressed in the light of positional cloning and positional candidate gene identification in humans. It summarizes the recent efforts in developing theories for fine-scale mapping of genes underlying complex genetic variations where the one-to-one relationship no longer exists between phenotype of the genetic disorders and the corresponding genotype. Dedicated to Dr. C. C. Tan for his 90th birthday.     

Transposon-dependent mutant phenotypes at the Notch locus of Drosophila

Many mutations at complex genetic loci in the fruitfly Drosophila melanogaster are associated with insertions of transposable elements. At the Notch locus, members of one class of insertion-associated mutations, termed glossy-like, produce a recessive viable, smooth-eye phenotype with mottled pigmentation. Members of a second class, facet, produce a recessive viable, rough-eye phenotype with homogeneous pigmentation. Both classes of mutations fail to complement Notch lethal mutations, so they behave as Notch alleles. Here we report that each glossy-like mutation is associated with an insertion of the same transposable element (flea). Each flea insertion occurs in the same orientation, but at different locations within intervening sequences of the Notch locus. In contrast, each facet mutation is associated with insertion of a unique, non-flea, transposable element. Insertions producing a facet phenotype and insertions causing a glossy-like phenotype can break Notch intervening sequences at precisely the same location. This suggests that the type of insertion element rather than its position within an affected gene is the primary determinant of the phenotype observed.     

Localization of cystic fibrosis locus to human chromosome 7cen-q22

Cystic fibrosis (CF) is the most common genetic disease in Caucasian populations, with an incidence of 1 in 2,000 live births in the United Kingdom, and a carrier frequency of approximately 1 in 20. The biochemical basis of the disease is not known, although membrane transport phenomena associated with CF have been described recently. Consanguinity studies have shown that the inheritance of CF is consistent with it being a recessive defect caused by a mutation at a single autosomal locus. Eiberg et al. have reported a genetic linkage between the CF locus and a polymorphic locus controlling activity of the serum aryl esterase paraoxonase (PON). The chromosomal location of PON, however, is not known. Linkage to a DNA probe, DOCR1-917, was also recently found at a genetic distance of approximately 15 centimorgans (L.-C. Tsui and H. Donnis-Keller, personal communication), but no chromosomal localization was given. Here we report tight linkage between the CF locus and an anonymous DNA probe, pJ3.11, which has been assigned to chromosome 7cen-q22.     

思茅松种子园遗传结构及遗传多样性

采用等位酶分析的方法对思茅松种子园内收集的4个思茅松群体进行遗传分析,以此阐述了思茅松种子园的遗传结构和遗传多样性状况。9种酶16个酶位点的遗传分析结果：思茅松种子园的多态位点比例（P）为73.5%;平均每个位点的等位基因数（A）为2.42;平均每个位点的等位基因有效数（Ne）为1.54;期望杂合度（He）为0.295;实际杂合度（H0）为0.181。结果表明思茅松种子园具有较广泛的遗传基因和遗传多样性;思茅松种子园的建立是思茅松遗传改良的有效途径之一。     

杉木地理种源的EST-SSR分子标记变异研究

研究采用EST-SSR分子标记对全国不同杉木种源区的42个代表性种源进行了地理种源分子标记的遗传多样性研究。实验结果表明,杉木种源水平上存在较高的遗传多态性。实验使用15个EST-SSR引物扩增出17个位点,共有52个多态性等位基因,每个位点平均具3.058 8个等位基因,平均每个座位的PIC为0.296。相对其他研究,该研究利用SSR标记在每位点检测到更多的遗传变异信息。以遗传距离10作为阀值时,42个杉木种源聚类分析可知,除了福建永春碧卿(编号2)和广西浦北(编号16)种源自成一类外,其他40个种源按从南到北、从东到西的地理分布被聚为四大类群,与以往的杉木种子区划研究结果有较高的吻合度。同时,研究也检测到SSR分子标记的等位基因频率在四大类群间存在着较大的变异,而且这些标记大多位于与植物抗逆性相关的功能基因的编码区域内。因此,笔者推测杉木的地理变异可能与这些基因的等位变异有关。     

Fitness reduction associated with the deletion of a satellite DNA array

Satellite DNA refers to a class of tandem repeats of very simple sequences, usually A + T or G + C rich, which form a satellite band on a CsCl gradient. Their ubiquity and abundance in higher eukaryotes have led to speculation about their functions. It has often been suggested that satellite DNAs are merely innocuous genetic parasites or comprise 'junk' DNA. The recent identification of an array of satellite DNA repeats as the Responder (Rsp) locus of Drosophila melanogaster provides a new perspective on these elements. Rsp is in the centromeric heterochromatin of most natural second chromosomes. It causes spermatids bearing it to degenerate after meiosis when the homologous second chromosome is a Segregation Distorter (SD) chromosome. That is, SD targets the Rsp locus on its homologue for destruction during spermatogenesis, causing meiotic drive. Why then does the Rsp locus, a large array of satellite repeats, exist at all? One plausible explanation is that its existence contributes to the fitness of flies bearing it, compensating for the loss through meiotic drive. A direct demonstration of the usefulness of any family of satellite DNA is to compare the fitnesses of individuals with and without it. Previously, such an experiment has been difficult because the absence of a characteristic phenotype has precluded an efficient selection of deletion mutations. In this report we attempt to demonstrate a fitness reduction associated with the deletion of Rsp satellite DNA as well as the life stages at which such a reduction occurs.     

A polymorphic DNA marker linked to cystic fibrosis is located on chromosome 7

Although cystic fibrosis (CF) is among the most common inherited diseases in Caucasian populations, the basic biochemical defect is not yet known. CF is inherited as an autosomal recessive trait apparently due to mutations in a single gene, whence the efforts made to identify the genetic locus responsible by linkage studies. Two markers have recently been identified that are genetically linked to CF: one is a genetic variation in serum level of activity of the enzyme paraoxonase, and the other is a restriction fragment length polymorphism (RFLP) identified with a randomly isolated DNA probe. We report here that the genetic locus DOCRI-917 defined by the cloned DNA probe is located on chromosome 7.     

不同地理种群杂色鲍的同工酶分析

采用聚丙烯酰胺凝胶垂直电泳技术，对采白海南三亚、香港和福建平潭3个野生杂色鲍种群，以及1个种源来自台湾的九孔鲍养殖群体共4个群体的6种同工酶系统进行分析，共检测到10个基因位点，其中2个为多态位点(多态位点比例为20％)，每个位点平均等位基因数为1．2；4个群体都不同程度地表现出纯合子过剩、杂合子不足，遗传变异量偏低．群体间遗传相似系数与遗传距离以及UPGMA聚类分析的结果表明：4个群体之间的遗传差异不大，遗传距离均小于0．01．属于种群差异水平．九孔鲍和杂色鲍的遗传差异达不到亚种水平．     

A pair of two－component regulatory genes ecrA1／A2 in S. coelicolor

Two-component genes are kinds of genetic elements involved in regulation of antibiotic production in Streptomyces coelicolor. DNA microarray analysis revealed that ecrA1/A2, which mapped at distant sites from red locus and encode respectively the kinase and regulator, expressed coordinately with genes of Red specific biosynthetic pathway, ecrA1 and ecrA2 gene-disruptive mutants were constructed using homogenotisation by reciprocal double crossover. Fermentation data showed that the undecylprodigiosin (Red) level of production was lower than that of wild-type strain. However, the change of the actinorhodin (Act) production level was not significant compared with wild type. Thus, these experiment results confirmed that the two-component system ecrA 1/A2 was positive regulatory element for red gene cluster.     

藏羚羊5个微卫星标记的多态性分析

藏羚羊是我国青藏高原的特有物种.为分析藏羚羊独特的遗传变异特征和核DNA遗传多样性,以5个微卫星标记对50只藏羚羊的等位基因多态性进行了研究.研究结果表明:5个微卫星标记共检测到92个等位基因,每个标记的平均等位基因数为18.4个(在16~23之间),平均有效等位基因数为11.1;5个微卫星标记的多态信息含量均在0.8573以上,为高度多态标记,其中L03标记的多态信息含量最高,达0.9372;各标记的观测杂合度在0.4898~0.9091之间,期望杂合度在0.8770~0.9504之间,平均期望杂合度为0.8990,属于高度杂合标记,遗传变异丰富.这些筛选出的多态性微卫星标记可应用于藏羚羊遗传多样性、遗传结构分析及遗传图谱的构建等工作.     

一种多值编码遗传算法的缺失基因复现方法

与二值编码遗传算法相比,基因缺失问题对多值编码遗传算法的全局搜索性能影响比较大.提出一种缺失基因复现和存活的变异方法,即根据字符集中的字符在种群中的缺失作为预选变异基因集,然后对待变异个体集进行预变异;选择高适应度个体的对应变异基因和基因位,使其在原待变异个体集中扩散.将该方法应用到多重选择背包问题的遗传算法中,通过仿真实验验证了该方法的有效性.     

不同品种马血清酯酶（Es）位点遗传距离聚类分析

通过对青海的湟中马，柴达木马，陕西的关中马，宁强马，广西百色马，贵州马，泰国马，阿拉伯马，日本吐噶喇马，英国纯血马，韩国赛马１１个品种血清酯酶位点的基因频率计算遗传距离，并进行聚类分析表明：Ｅｓ位点是不同品种马遗传分化的主要位点，对探索马的分类和起源具有重要意义。     

A family of candidate taste receptors in human and mouse

The gustatory system of mammals can sense four basic taste qualities, bitter, sweet, salty and sour, as well as umami, the taste of glutamate. Previous studies suggested that the detection of bitter and sweet tastants by taste receptor cells in the mouth is likely to involve G-protein-coupled receptors. Although two putative G-protein-coupled bitter/sweet taste receptors have been identified, the chemical diversity of bitter and sweet compounds leads one to expect that there is a larger number of different receptors. Here we report the identification of a family of candidate taste receptors (the TRBs) that are members of the G-protein-coupled receptor superfamily and that are specifically expressed by taste receptor cells. A cluster of genes encoding human TRBs is located adjacent to a Prp gene locus, which in mouse is tightly linked to the SOA genetic locus that is involved in detecting the bitter compound sucrose octaacetate. Another TRB gene is found on a human contig assigned to chromosome 5p15, the location of a genetic locus (PROP) that controls the detection of the bitter compound 6-n-propyl-2-thiouracil in humans.     

Genetic homogeneity between acute and chronic forms of spinal muscular atrophy

The childhood-onset spinal muscular atrophies (SMAs) describe a heterogeneous group of disorders that selectively affect the alpha motoneuron. We have shown that chronic childhood-onset SMA (SMA II and III) maps to a single locus on chromosome 5q. Acute SMA (SMA Type I/Werdnig-Hoffmann/severe/infantile) is the main cause of heritable infant mortality. Mapping the acute SMA locus by conventional methods is complicated by the rapidly fatal course of the disease and its recessive mode of inheritance. We present here the typing of four inbred acute-SMA families with DNA markers on chromosome 5q and analysis of these together with acute families from our previous study to demonstrate genetic homogeneity between the acute and chronic forms of SMA. The data indicate that the acute SMA locus maps to chromosome 5q11.2-13.3. Two families seem unlinked to 5q markers, raising the possibility of genetic heterogeneity or disease misclassification within the acute and chronic family sets.     

基于混合算法求解指派问题

本研究建立了指派问题的数学模型,提出了以遗传算法和蚁群算法相结合的思想及其解决方案．算法主要是将每一个任务作为一个基因位形成染色体,以遗传算法控制寻优方向,更适宜解决组合优化问题．实验结果表明,使用此算法解决指派问题,提高了搜索效率,能够在短时间内找到最优分配方案,证明该算法是可行的．