无芒隐子草全基因组水平全长LTR反转录转座子鉴定及其中断基因分析

LTR反转录转座子是植物基因组内大量可移动的遗传因子,是基因组的重要成分之一。无芒隐子草基因组大小为543 M,全基因组中共鉴定出了299079个LTR反转录转座子,占全基因组的26.54%,但是缺少无芒隐子草全长LTR反转录转座子的研究。基于无芒隐子草全基因组序列,筛选出具有潜在活性的全长LTR反转录转座子845个,其中有410个属于Gypsy超家族,435个属于Copia超家族。对这些序列进行了系统进化树的构建和插入时间的分析,发现全长LTR反转录转座子的大量转座发生在4百万年内,插入时间较近,插入高峰期是1~1.5百万年间。筛选出被全长LTR反转录转座子中断的基因有183个,145个被中断的基因得到了GO功能注释,分析了被中断基因在不同干旱胁迫处理下的基因表达模式。对反转录转座子的鉴定有助于深入了解无芒隐子草的进化过程,为无芒隐子草全长LTR反转录转座子与中断基因的后续研究奠定基础。     

mariner 转座子及其在昆虫种系转化中的应用

转座子是不需要同源重组便能在基因组内和基因组间移动的遗传学顺式元件.mariner是最简单的真核转座子,在昆虫中广泛分布.mariner转座子的转座作用只与转座酶有关,是一种很有发展前景的转基因载体,可以实现异源昆虫间的基因转移,产生稳定遗传的转基因品系.     

地熊蜂基因组中具有潜在活性的转座子鉴定

转座因子(TEs)是真核生物基因组的主要序列成分,对真核生物基因组的结构、功能及进化具有重大影响。近年来,虽然有关昆虫转座子的研究在不断增加,并且科学家成功地应用转座子进行了功能基因的挖掘,但相关研究主要集中于双翅目的果蝇中。本研究利用生物信息学方法,基于de novo预测和结构预测两种策略,对地熊蜂参考基因组中的转座子进行了详细鉴定、分类和注释,并鉴定出潜在活跃的转座子。结果显示:虽然转座子序列仅占地熊蜂基因组全部序列的3.74%,但其超家族种类繁多,鉴定出的33282个转座子分属于22个超家族。本研究鉴定出2种具有潜在活性的MITE转座子,它们很可能正在地熊蜂基因组中发生转座。本研究为利用活跃的转座子创制地熊蜂的突变体库进而挖掘熊蜂的功能基因奠定了重要基础。     

PiggyBac转座子及其在家蚕中的应用

转座子可以由染色体的一个位置移动到另外位置,改变原有基因的结构和排序,从而导致基因改变。转座子可分为2大类,第1类转座子又有多种类型,这类转座子能以染色体DNA转录形成的RNA为模板,经反转录酶作用合成DNA并插入到基因组中;第2类转座子则直接在基因组中来回移动,不形成RNA,也与反转录酶的作用无关。用于昆虫重组的转座子几乎都是第2类转座子,其末端具有反向重复序列,中间部分为转座酶基因,此基因可产生转座酶,使末端重复序列与其内侧的目标序列移动,即将目标序列部分切出,并重组到染色体的其它部位上。因此,可利用这类转座子进行转…     

piggyBac转座子在哺乳动物中的应用

转座子(transposon)是存在于生物体基因组中的可移动的DNA片段,能够影响基因的结构和功能,广泛存在于生物演化过程中。转座子通过切离和粘贴机制介导外源基因的插入,是研究基因功能,制备转基因动物及基因治疗的优良载体。目前在哺乳动物中转座活性较高且研究最多的是"睡美人"转座子和piggyBac(PB)转座子。前者是目前临床前基因治疗研究中使用最为广泛的转座子,但存在剂量抑制效应和转座效率低等缺陷。而PB转座子可克服剂量抑制效应,且转座高效,转基因载量大,因此在哺乳动物中的应用越来越广泛。作者就PB转座子的作用机制、影响因素及在哺乳动物中的应用现状等进行报道。     

禽类转座子的研究进展

转座子作为一段可移动的DNA序列,对于生物体的基因组进化和物种分化发挥着重要作用。近年来,转座子在生物突变体制备、转基因研究和基因治疗等领域展现出了非常大的潜能。然而目前关于动物转座子的研究主要集中在哺乳动物,禽类转座子的相关研究较少。禽类基因组内的转座子元件具有含量少、多样性低等特点,同时禽类转座子在基因组中的分布也与哺乳动物有很大差异。文章综述了各类转座元件的结构特征和挖掘方法以及禽类基因组中转座子的种类和特点,并对禽类基因组内转座元件的研究进展和存在的问题进行阐述,旨在提高禽类转座子研究的重视程度,为禽类转座子的后续研究提供理论参考。     

微孢子虫转座元件的研究现状

转座子是基因组中可以从一个位点转移到另一个位点并进而影响到与之相关的基因功能的遗传因子,是造成基因组内突变的主要原因之一。本文针对兔脑炎微孢子虫、蝗虫微孢子虫、家蚕微孢子虫、比氏肠细胞内原虫、Spraguealophii、Edhazardia aedis以及Brachiola algerae等物种的已发布的转座元件序列进行概括性总结,并对转座元件在微孢子虫基因组进化中的作用进行了分析。     

卵泡抑制素基因在猪成纤维细胞中过表达研究

利用piggy Bac转座子将卵泡抑制素(follistatin)基因整合入猪基因组中,检测follistatin基因表达情况及其对细胞分化基因p53和desmin的影响。结果表明:piggy Bac转座子将follistatin基因转座整合入猪基因组中,整合入基因组的位点均为TTAA位点。整合后的follistatin基因可以正常的转录表达,follistatin的过表达引起p53和desmin基因的表达上调。     

哺乳动物转基因载体——piggyBac转座子

piggyBac转座子具有识别位点特异性5'-TTAA-3',剪切和插入都不留下印迹,且高效转座。基于piggyBac转座子的特性,借助载体系统,已应用于哺乳动物转基因的研究。此外,piggyBac转座子还应用于基因诱导突变和基因治疗等领域。RNAi技术作为基因功能研究的一个工具,在应用于克服畜牧业中家畜的生产繁殖障碍等方面已取得一定研究成果。本文对piggyBac转座子的结构和特性、转座机制及影响因素和在动物中应用等方面进行总结,为RNAi技术借助piggyBac转座子用于哺乳动物转基因提供理论依据。     

Mariner转座子简介

转座子是自然发生的 ,能够从一个位点转移到另一个位点的遗传因子 ,它存在于染色体 DNA上。转座子的基本成分是一个基因 ,该基因编码转座作用所需要的酶—转座酶 ,以及供转座酶识别的侧翼序列。自主的因子编码转座酶的功能拷贝 ,拥有介导转座的识别序列。非自主的因子通常含有转座酶的变异拷贝 ,却又保留识别序列 ,因此 ,其它来源的转座酶能够移动非自主因子。转座子被频繁用作基因突变的手段 ,转座子标签在基因克隆中极其有效 ,是通过变异表型和特定的转座子的相关来克隆基因的 ,转座子插入到特定的基因 ,或插入到由转座子切除引起的缺失…     

苜蓿遗传图谱构建及其应用

苜蓿是世界上最重要的豆科牧草之一,苜蓿遗传图谱构建是解析重要农艺性状(QTL)遗传特性和基因连锁分析的前提条件。由于复杂的四体遗传特性,目前已构建成功的苜蓿遗传图谱大多数是二倍体苜蓿,四倍体栽培苜蓿遗传图谱较少。本研究就苜蓿遗传图谱构建研究已取得的成就、图谱绘制过程中的限制因素、解决策略和已有图谱的特征等问题进行了回顾和讨论;对苜蓿遗传图谱研究,特别是构建四倍体苜蓿遗传图谱,在揭示苜蓿遗传特性和定位重要农艺性状相关基因位点(QTL)方面的应用现状和重要意义进行了论述,就苜蓿遗传图谱在苜蓿分子标记辅助育种中的应用前景进行了展望,并就我国苜蓿育种现状和开展苜蓿遗传图谱构建研究提出了一些建议。     

The role of reproductive technologies in breeding schemes for livestock populations in developing countries

The world is faced with the challenge to meet the increasing demand for livestock products while conserving animal genetic resource diversity and maintaining environmental integrity. Genetic improvement of local breeds can help to improve the livelihood of the livestock keepers, to increase the production of animal products and to conserve genetic diversity. Implementing breeding schemes in developing countries has proven to be very difficult. The objective of this paper is to discuss the role of reproductive technologies for the creation and dissemination of genetic improvement in livestock populations in developing countries. In the paper opportunities are discussed for implementing breeding schemes which minimize the need for extensive pedigree and performance recording. It is shown that genetic progress can be generated in a small population. Community-based breeding schemes offer a good starting point for involving farmers in improving local breeds. Artificial insemination to exchange genetic material between communities offers an opportunity to increase the rate of genetic improvement while restricting the rate of inbreeding. Furthermore, artificial insemination is a promising technique for dissemination of genetic gain to producers at a relatively low cost. Opportunities to use semen sexing in a crossbreeding scheme are presented. It is concluded that tailor-made solutions and long-term commitment are needed in order to meet the needs of farmers to increase their livelihoods and to meet the needs of the growing population of consumers.     

Genetic selection in farmed deer

Selection is the major tool used by breeders to improve the genetic quality of their livestock. Traditional methods of selection are well proven and useful in improving the economic merit of livestock. The performance of an animal is affected by its genetic quality and by the environment in which it is reared. While environmental improvement is expensive and requires continuous inputs, genetic improvement is cumulative and permanent, provided that selection is maintained. To select an animal on its genetic merit account must be taken of the environmental effects on its performance. Comparisons between the performance of animals on different farms or in different years are not valid unless they have genetic material in common. The speed at which genetic improvement is passed on to the rest of a population is affected by the variation and heritability of the traits being selected, the selection intensity and the generation interval. The deer population in the United Kingdom has a high degree of variation for important traits but the selection intensity is low and the generation intervals are larger than in other farmed species. Central performance testing, group breeding schemes and the use of artificial insemination are tools which will be important in the genetic improvement of farmed deer.     

牛奶的中红外光谱相关指标及遗传规律研究进展

中红外光谱分析技术(MIRS)作为一种快速且经济的检测手段广泛应用于生产,中红外(MIR)光谱在本质上可以反映牛奶特征。MIR光谱整体上是一条具有低中高遗传力的曲线,但并非所有MIR区域都具有遗传意义,应深入挖掘光谱数据具有的高遗传变异,提取可用于遗传育种的有效区域,得到筛选光谱信息区域的最佳方法。在标准预测模型基础上,获得的牛奶组分预测值具有遗传变异性,总体上呈中高遗传力,可进行遗传选择或对相关性状进行间接选择;借助MIRS挖掘一些新型经济性状。本文对牛奶MIR光谱相关指标遗传规律进行综述,以期为选种选育提供理论基础。     

Evaluation of recent changes in genetic variability in Japanese thoroughbred population based on a short tandem repeat parentage panel

The integrity of thoroughbreds is maintained under strict regulation involving DNA parentage testing, which is robust in a population with high genetic variability. The genetic variability of the thoroughbred population is possibly fluctuating because of selective breeding that has focused on adaptations for racing performance. To monitor genetic variability within the population and the effectiveness of short tandem repeat (STR) parentage testing, we investigated allele frequencies and the exclusion probability (PE) of 16–17 loci of a parentage panel in the Japanese thoroughbred population over 15 years. Expected heterozygosities (He) of 14 loci indicated a decreasing trend, and the average He of the population decreased significantly. Low genetic variability was possibly induced by a decrease in population size and a selective breeding bias. Four loci showed both a significant increase in allele frequency and a significant decrease in He; it is assumed that those loci were affected by positive selection for racing performance. There was a significant decrease in the PE because of the changes in genetic variability; however, it has remained over 0.99995. The current STR panel is still effective for parentage control, but it will be necessary to continuously monitor genetic variability, which has decreased over 15 years.     

单核苷酸多态性的研究进展

染色体的某个位点上存在单个碱基的变化 ,称为单核苷酸多态性 ,即SNP。SNP是继限制性片段长度多态性和微卫星多态性以后 ,近年来出现的第三代遗传标记 ,广泛用于基因定位、克隆和遗传多样性研究。本文综合介绍了单核苷酸多态性的遗传特性、功能、研究意义及其在畜牧业中的应用     

Inbreeding and genetic diversity in dogs: results from DNA analysis

This review assesses evidence from DNA analysis to determine whether there is sufficient genetic diversity within breeds to ensure that populations are sustainable in the absence of cross breeding and to determine whether genetic diversity is declining. On average, dog breeds currently retain approximately 87% of the available domestic canine genetic diversity. Requirements that breeding stock must be 'clear' for all genetic disorders may firstly place undue genetic pressure on animals tested as being 'clear' of known genetic disorders, secondly may contribute to loss of diversity and thirdly may result in the dissemination of new recessive disorders for which no genetic tests are available. Global exchange of genetic material may hasten the loss of alleles and this practice should be discussed in relation to the current effective population size of a breed and its expected future popularity. Genomic data do not always support the results from pedigree analysis and possible reasons for this are discussed.     

The role of genetic engineering in livestock production

In this paper we discuss the use of genetic engineering in livestock production. We examine the main two different aspects of genetic engineering: cloning and transgenesis. After commenting what has been expected from both techniques in livestock production in the last 25 years, the practical difficulties for implementing cloning and transgenesis are examined. Apart from technical difficulties, problems derived from the detection of genetically superior animals and evaluation of the clones and the transgenic animals make these techniques less interesting than they appear to be. Most of the observed variability of the economically interesting traits is not genetic, genetic evaluation needs a large number of animals and cloning success will represent a serious loss of genetic variability and the loss of the flexibility needed for markets in constant evolution. There is a risk in transgenic animals of production of new intermediate biochemical products that may be toxic, allergenic or carcinogenic. The benefits produced by transgenic animals hitherto hardly justify this risk. The expectations that genetic engineering produced 25 years ago should be re-examined, considering the risks and the high investment required.     

Genetic diversity decreases as population density declines: Implications of temporal variation in mitochondrial haplotype frequencies in a natural population of Tscherskia triton

Although the spatial genetic differentiation that occurs in animal populations has been extensively studied, information on temporal variations in genetic structure and diversity is still lacking, especially for animals with oscillating populations. In the present study, we used the mtDNA D‐loop sequence to assess the temporal genetic variation in samples from six successive years for the greater long‐tailed hamster, Tscherskia triton. Sampling was carried out between 1998 and 2003 in cropland on the North China Plain, China. A total of 108 individuals were analyzed. The temporal samples showed a high level of genetic diversity. Substantial genetic changes in haplotype frequencies over time were detected for the hamster population. Random genetic drift and migration are likely to be the major factors responsible for the observed temporal pattern. The genetic diversity of the hamster population was higher in years with higher population density, and lower in years with lower population density. The result supports our hypothesis that genetic diversity decreases when population density declines in animals whose population oscillates greatly between years. The combined effects of inbreeding and genetic drift caused by reproduction, dispersal and population size might play important roles in the observed changes in genetic structure and diversity between years.     

Maximization of total genetic variance in breed conservation programmes

The preservation of the maximum genetic diversity in a population is one of the main objectives within a breed conservation programme. We applied the maximum variance total (MVT) method to a unique population in order to maximize the total genetic variance. The function maximization was performed by the annealing algorithm. We have selected the parents and the mating scheme at the same time simply maximizing the total genetic variance (a mate selection problem). The scenario was compared with a scenario of full-sib lines, a MVT scenario with a rate of inbreeding restriction, and with a minimum coancestry selection scenario. The MVT method produces sublines in a population attaining a similar scheme as the full-sib sublining that agrees with other authors that the maximum genetic diversity in a population (the lowest overall coancestry) is attained in the long term by subdividing it in as many isolated groups as possible. The application of a restriction on the rate of inbreeding jointly with the MVT method avoids the consequences of inbreeding depression and maintains the effective size at an acceptable minimum. The scenario of minimum coancestry selection gave higher effective size values, but a lower total genetic variance. A maximization of the total genetic variance ensures more genetic variation for extreme traits, which could be useful in case the population needs to adapt to a new environment/production system.