基因组选择在家畜改良上的研究进展

基因组选择（GS）是全基因组范围内的分子标记辅助选择,目前被证明是利用DNA标记信息改善复杂性状最有效的方法。本文简要概述了基因辅助选择以及标记辅助选择;重点介绍了GS,包括GS的实施策略与育种值估计方法,GS的准确性获得以及对GS方法的比较,总结了当前家畜上利用GS加速遗传改良的应用进展;并对家畜在GS上的应用前景进行展望。     

与泌乳性状有关的分子遗传标记的研究进展

泌乳性能是产奶家畜的重要生产经济性状．也是典型的由微效多基因控制，并受环境因素影响的数量性状。用遗传标记对家畜进行选择可以达到提高育种值的准确性和早期选种的目的。     

遗传标记简介

１．遗传标记的概念及用途遗传标记从广义上理解为生物体内受基因控制的全部可变异性状，且可用有效方法加以测定和度量；从狭义上理解为染色体已知部位的一个标记位点，通常指核酸水平上的遗传标记。利用遗传标记可进行遗传分析，检测质量性状和数量性状基因位点及对其进...     

畜禽遗传评定中QTL信息的利用及实践

迄今为止,畜禽绝大部分经济数量性状的遗传进展都是利用表型和系谱信息通过传统的数量遗传学方法取得的。控制数量性状的多基因一直被作为一个遗传整体用统计学方法加以研究和分析,在遗传评定中没有利用任何影响数量性状的遗传位点信息,从而造成评定结果准确性不高、遗传进展缓     

远交群体数量性状基因位点定位的原理

1　引言数量性状基因位点的定位是各种遗传操作的基础 ,如标记辅助选择、基因克隆和转基因动物等。可以预计 ,数量性状基因位点的定位将是今后一段时间内家畜育种工作的重要内容 ,这必将提高家畜育种的效率。利用遗传标记进行数量性状基因位点定位 ,为家畜育种开辟了一条新的途径 ,长期以来由于缺乏合适的遗传标记 ,育种工作者只能利用血型、血蛋白及酶的多态性作为遗传标记进行研究 ,因而进展缓慢。新一代遗传标记微卫星的出现 ,使家畜数量性状基因位点定位的研究再度成为热点。本文将进一步讨论在远交群体中进行数量性状基因位点定位的统…     

利用基因组信息提高畜禽生产性能研究进展

为了满足人们对畜产品需求的快速增长，必须在加快畜禽产业发展的同时把对环境的影响降到最低，提高畜禽遗传特性有望促进这一问题的解决。进入21世纪以来，以基因组选择为核心的分子育种技术迎来了发展机遇，利用该技术可实现早期准确选择，从而大幅度缩短世代间隔，加快群体遗传进展，并显著降低育种成本。虽然在某些畜种中（如奶牛），基因组选择取得了成功，群体也获得较大遗传进展，但仍无法满足快速增长的需求。因此，亟需寻找能够进一步加快遗传进展的方法。研究表明，在SNP标记数据中加入目标性状的已知功能基因信息，可以提高基因组育种值预测的准确性，进而加快遗传进展。而挖掘更多基因组信息的同时，开发更优化的分析方法可以更有助于目标的实现。文章总结了主要畜禽物种的可用基因组数据，包括牛、绵羊、山羊、猪和鸡以及这些数据是如何有助于鉴定影响重要性状的遗传标记和基因，从而进一步提高基因组选择的准确性。     

限制性片断长度多态性与家畜的遗传改良

限制性片断长度多态性与家畜的生产性能存在相关,这种相关主要是由于限制性片断基因与数量性状位点存在连锁关系所引起。通过对与标记位点连锁的家畜近交系子二代数量性状分析,可获得数量性状位点的主效应和显性效应。同时,借助于限制性片断或已知片断的辅助选择,可使家畜的经济性状得到遗传改进。     

家畜全基因组关联分析研究进展

全基因组关联分析（genome-wide association study,GWAS）是一种研究经济性状候选基因的分析方法。近年来,随着家畜全基因组测序的完成,大量的单核苷酸多态性（single nucleotide polymorphisms,SNPs）被标识,GWAS也越来越多地应用于家畜重要性状的研究领域中,在动物遗传育种中,通过对家畜基因组进行GWAS分析研究,找到控制家畜主要经济性状的重要SNPs,从而挖掘重要经济性状的候选基因。作者详细综述了GWAS的分析方法及其在重要家畜育种中的研究进展。GWAS分析方法包括基因组控制法（genommic control）、分层分析法（stratification analysis）、主成分分析法（principal components analysis,PAC）和混合线性模型分析法（mixed-linear-model association,MLMA）,通路分析方法包括非核算法（基因功能富集分析（gene set enrichment analysis,GSEA）和分层贝叶斯优取（hierarchical Bayes prioritization,HBP））和核算法。依据不同的目标性状选择合理的分析方法,提高GWAS分析结果的准确性,为进一步利用GWAS分析各种性状的遗传基础提供合理的借鉴。     

近年来动物遗传育种领域的一个热点——全基因组选择

基因组选择近年来成为动物遗传育种领域的一个热点,并有望在将来引起传统育种方式产生重大的变化。猪的基因组选择目前主要是利用基因组信息和猪屠宰、繁殖性状的生产记录对猪进行选择。猪的育种值并不能直接观察得到,而是利用个体本身和亲属信息(后裔、同胞及祖先)估计个体的育种值。所利用的信息越多,育种值估计的准确性越高。基因组选择的基本思想是基因分型个体的DNA信息包括来自其他远缘及无关基因分型个体的信息。     

母猪繁殖性状分子遗传标记研究进展

母猪的繁殖性状包括产仔数、初生重、初生窝重、断乳窝重、初产日龄和产仔间隔,其遗传力为0.1左右,属于低遗传力性状.用常规遗传选育方法对低遗传力性状选择难以获得理想遗传进展.将控制经济性状的重要基因或标记用于标记辅助选择能够提高低遗传力性状改良的遗传进展.因此,文章对已经鉴定出的影响母猪繁殖性状的相关基因进行综述,总结了...     

Genetic evaluation using parentage information from genetic markers

Genetic evaluation relies on pedigree information to account for the trait information on individuals and their relatives. Recording pedigrees may place unfavorable restrictions on the management of breeding populations, such as the use of single-sire mating groups and the observation of parturition. The use of DNA marker information is an alternative method to identify parents, but it is difficult to assign the parents unambiguously for all progeny in extensively farmed livestock without the use of very many markers. We present methods that use DNA information on parentage within a genetic evaluation system that allow for genotyping errors and for the parentage information to be incomplete, with probabilities assigned to possible parent pairs (i.e., fractional parentage assignment). Two of these methods use a computing strategy that circumvents the high memory requirements associated with the application of previous methods designed for use with fractional parentage assignment. This strategy has an additional advantage of allowing the same statistical models to be used in the evaluation as with recorded pedigrees. The use of DNA marker-based parentage for genetic evaluation is associated with lower genetic gain (at the same survival levels) than by using the true pedigree. This decrease in gain depends on a number of factors, including trait heritability and the DNA markers used. The methods we have described show how DNA marker information could be used to replace traditional pedigree recording.     

Genetic selection and conservation of genetic diversity*

For 100s of years, livestock producers have employed various types of selection to alter livestock populations. Current selection strategies are little different, except our technologies for selection have become more powerful. Genetic resources at the breed level have been in and out of favour over time. These resources are the raw materials used to manipulate populations, and therefore, they are critical to the past and future success of the livestock sector. With increasing ability to rapidly change genetic composition of livestock populations, the conservation of these genetic resources becomes more critical. Globally, awareness of the need to steward genetic resources has increased. A growing number of countries have embarked on large scale conservation efforts by using in situ, ex situ (gene banking), or both approaches. Gene banking efforts have substantially increased and data suggest that gene banks are successfully capturing genetic diversity for research or industry use. It is also noteworthy that both industry and the research community are utilizing gene bank holdings. As pressures grow to meet consumer demands and potential changes in production systems, the linkage between selection goals and genetic conservation will increase as a mechanism to facilitate continued livestock sector development.     

Genetic conservation of five endangered Spanish donkey breeds

The genetic diversity of most livestock species is being reduced, and it is not possible to preserve all of these livestock breeds. In order to preserve as much of the genetic diversity as possible, we must first have a robust method of measuring genetic diversity among breeds. Three different methods of study that graphically represent relationships among breeds are presented; Weitzman's method, principal component analysis (PCA) and a neighbour‐joining tree with allele sharing. Diversity was evaluated on the basis of 15 microsatellite markers typed over a total of 513 DNA samples collected from five Spanish donkey breeds. Breed differentiation was confirmed by the clustering based on the genetic distances between individuals, which essentially grouped all individuals in discrete clusters. The genetic distance among breeds was used to measure the global diversity of the set in breeds considered, and to evaluate the marginal loss of diversity attached to each breed. The Catalana breed appeared to be the most ‘unique’ in the set considered. In addition to this, the usefulness of global evaluations of diversity using molecular markers to choose breeds is worthy of conservation.     

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.     

试论家畜遗传资源保护的原理与方法

本文论述了家畜遗传资源保护的理论和实践方法，部分讨论了家畜遗传资源保护的目标及维持品种间和品种内的多样性以及认识单个品种的价值。在一些文章中，为实现这一目标提出过数种不同战略，包括Weitzman提出的多样性度量方法，这在本文中是一个基础概念。尽管，关于决策制定的高深而详细的方法在一些文献中讨论过，但这一概念在国家或国际以及非政府组织中则是非常简单的，甚至仅仅局限于群体数量，而实际上，这一概念讨论的是决策的制定基于一个品种的全球多样性。因而，相应的决策制定和实际行动应和国际水平相符合，一些正确的决策尺度将能很好地提高保护投资的效率。家畜保护应当建立在更宽广的客观目标，即尽可能的反映保护的一系列品种的未来价值，这包括品种间、品种内多样性、特殊性状、主要品种的文化和科学价值。因此，一个重要的议题是如何引申出评价品种价值和一个品种濒危程度所需要的若干参数，一般来说，能获得准确的数值是困难的，基于不确定值而制定的保护策略显然具有一定的风险，而Bayesian（贝叶斯）决策理论将是一个好的选择，这种最优选择的分配模式和保护行动的执行建立在Weitzman提出的期望多样性概念而得以引伸。     

加强畜禽遗传资源保护与利用思路建议

本文对我国畜禽遗传资源保护已开展工作和取得的成绩进行了全面总结,分析了存在的主要问题,提出了进一步加强畜禽遗传资源保护工作的思路建议.     

畜禽某些疾病的遗传控制与抗病育种

提高畜禽的抗病性与健康水平已成为当今提高畜牧生产的重要途径。本文从抗病遗传机制出发 ,叙述了单基因与多基因遗传病研究进展 ,探讨了抗病育种的可能途径。     

畜禽选择方法的发展对选择效率的促进

随着科学技术的发展,畜禽的选择及遗传评定方法也在不断提高,并经历了从经验式育种到全基因组选择的巨大演变与发展,这种发展也不断地改进了选择效率。综述了畜禽选择方法的发展历程,并对各种选择方法作了简要评述。     

Fine-Scale Spatial Genetic Structure in Perennial Grasses in Three Environments

Past research has shown that changes in grazing-resistance traits may be associated with genetic changes in plant populations. Little is known about spatial genetic relationships within plant populations (spatial genetic structure) and any grazing effects on these relationships. Here we present observations of the fine-scale spatial genetic structure in three grass species in semiarid environments (Arizona, Mexico, and Argentina). In each environment, populations of a dominant grass species were sampled from two sites with contrasting livestock grazing histories. Plant genotypes were described with the use of amplified fragment length polymorphism markers. In Arizona, populations of sideoats grama (Bouteloua curtipendula var. caespitosa Gould and Kapadia) differed in that one has never experienced livestock grazing, whereas cattle have grazed the other. In the other two environments, populations exposed to long-term heavy grazing were examined, along with those that experienced either moderate grazing (Mexico, blue grama [Bouteloua gracilis {Willd. ex Kunt} Lag. ex Griffiths]) or extended exclusion of livestock (Argentina [Poa ligularis Nees ex Steud.]). Based on independent analysis of each population, we observed no differences in average gene diversity between populations of each species. With the use of analysis of molecular variance we found slight but significant genetic differentiation between populations with different grazing histories in Arizona and Argentina. Significant genetic structure was present in all populations and indicated an inverse relationship between spatial and genetic distance. Interestingly, this relationship was most pronounced in the cattle-free sideoats grama population, suggesting larger genetic neighborhood areas in the absence of livestock. Less distinct differences in spatial genetic structure associated with grazing history were evident in the other two species. We hypothesize that livestock grazing may lead to increased homogeneity in genetic structure at the landscape scale. Effectively examining this hypothesis presents many experimental challenges.     

母猪母性行为及其遗传研究进展

家畜生产中,母性行为是一个非常重要的性状。母猪选择中都注重其产仔数的提高,在提高产仔数同时,还要求它们能够成功喂养所产后代,因此改善提高母猪母性行为性状对仔猪的成活及生长至关重要。母猪的母性行为性状主要是指对仔猪尖叫反应、恐惧行为、攻击行为、育幼行为等,这些性状一般部分地受遗传控制,故可选择提高母性行为性状以改善母猪性能。本文综述了母猪母性行为性状及其遗传研究进展,讨论了母性行为与仔猪成活率之间的关系以及在选择、生产、管理中的应用;并对母性行为遗传研究提出一些看法,以期对国内家畜行为遗传研究起到推动作用。