影响家畜繁殖性状主基因的研究进展

主基因是指能对数量性状产生巨大效应的单个基因或座位。家畜繁殖性状属低遗传力数量性状。通过对家畜繁殖性状主基因或其候选基因的定位、研究, 有利于进一步认识繁殖性状遗传机理, 加快对繁殖性状的改良速度。目前在猪上对FSHβ、ESR基因, 在绵羊上对FecB、FecX和BMP15等基因研究较多。     

绵羊繁殖性状候选基因的研究进展

目前，研究发现的影响绵羊繁殖性状的候选基因主要有四个，即FecB,FecX1,FecX和FecX2w，本文就这四个基因的发现，定位及其研究进展作一系统阐述。     

奶牛性别鉴定的研究与应用

 以控制部分绵、山羊品种高繁殖力的BMPR IB、BMP15和GDF9基因为候选基因,采用PCR RFLP方法分析闽东山羊BMPR IB,BMP15 和GDF9 基因多态性与繁殖性状的关系。研究发现：多胎品种闽东山羊及南江黄羊在BMPR IB 基因的相应位置上并未发生与Booroola Merino 羊相同的突变,同时也未检测到BMP15 的FecXI, FecXH , FecXB基因及GDF9的FecGH 基因,因此排除了这5个突变位点影响闽东山羊高繁殖力性状的可能性。然而,由于闽东山羊的BMPR IB、BMP15、GDF9 的全基因序列信息的缺乏,尚不能完全断定3个基因对闽东山羊高繁殖力性状没有影响。     

与绵羊多胎性状有关的FecB和FecX基因研究进展

FecB和FecX基因是在研究绵羊多胎性状中发现的2个关键基因,对其深入研究将会对绵羊以及家畜遗传育种发挥积极的推动作用.从FecB和FecX基因的生理效应、基因定位等方面进行综述,以期为相关研究提供参考.     

绵羊多胎基因有效利用方式与选育

绵羊多胎性状主效基因的研究,不仅可以阐明多胎绵羊生理和遗传机理,得出多胎性状遗传模式,而且有助于家畜选种选育,提高绵羊繁殖力。FecB和FecX基因是在研究绵羊多胎性状中发现的2个关键基因,主要分析了这两个基因的生理效应、基因定位等方面的内容,以期对绵羊的遗传育种起到积极的作用。     

绵羊多胎基因及相关遗传标记研究进展

绵羊的繁殖性状受多基因控制,文章综述了现已发现并证明的多胎基因,如FecB基因、BMPR-IB基因、FecX基因及相关遗传标记.并阐述了这些基因的发现、定位、遗传效应及调控机制.探讨绵羊多胎基因的调控机制.     

绵羊繁殖性状候选基因调控的研究进展

绵羊的繁殖性状受多基因调控,作者简要综述了现已发现并证明的主效基因和QTL位点（如FecB、FecX^I、FecX^H和FecX^2W等）。通过分析这些基因或QTL位点的作用、基因定位、生理效应、遗传方式及遗传效应等,从而为探讨绵羊多胎性状的基因调控规律提供理论依据。     

绵羊多胎基因有效利用方式与选育

绵羊多胎性状主效基因的研究,不仅可以阐明多胎绵羊生理和遗传机理,得出多胎性状遗传模式,而且有助于家畜选种选育,提高绵羊繁殖力。FecB和FecX基因是在研究绵羊多胎性状中发现的2个关键基因,主要分析了这两个基因的生理效应、基因定位等方面的内容,以期对绵羊的遗传育种起到积极的作用。     

绵羊多胎性状基因的研究进展

绵羊的多胎性状是养羊业获得更多经济效益的重要途径.随着分子育种技术的发展和高精细基因图谱的不断完善,世界各地的研究者对多胎性状的基因进行了探讨,发现并证明了一些与多胎有关的基因:FecB、FecX、GDF9、Woodland、Thoka和Lacaune等,并对这些基因的来源、遗传方式及效应、候选基因、生理效应等方面进行了研究.现将绵羊多胎性状基因的研究进展综述如下.     

鸡QTL定位的研究进展

鸡的大多数重要经济性状均属于数量性状,研究鸡数量性状遗传对鸡育种具有十分重要意义。数量遗传性状变异位于染色体特定位点的连锁编码基因被称为数量性状位点(quantitative trait locus,QTL)。近年来,大量研究揭示了鸡QTL的基本特征,剖析了重要经济性状的遗传基础,已经精细定位和克隆了鸡特定数量性状基因,给鸡资源保护遗传改良提供了新策略。文章综述了QTL定位的理论基础及鸡QTL定位的研究进展,并对鸡QTL研究的趋势进行了展望。     

黄淮山羊微卫星多态性及其与产羔数相关性的研究

以绵羊FecB、GDF9和BMP15为候选基因,同时选择绵羊6号染色体与FecB基因紧密连锁的6个微卫星标记,分析其在黄淮山羊中的多态性及其与产羔数的关系。结果表明:在黄淮山羊中均未发现FecB、GDF9基因和BMP15基因突变。微卫星Lscv043、BMS2508、300U、GC101均为多态位点;而GC101与产羔数具有较强的相关性,在GC1013种基因型中200bp/238bp基因型群体对应的第1胎产羔数和第2胎产羔数均显著高于其他2种基因型群体的对应产羔数(P<0.05);但是各基因型群体之间第3胎产羔数差异不明显;同样基因型200bp/238bp对应群体的平均产羔数极显著高于其他2种基因型群体的平均产羔数(P<0.01)。其他位点的不同基因型群体之间产羔数差异均不明显。这些结果表明,FecB基因所在区域位点对山羊产羔数亦具有一定影响,可以作为山羊早期选育的理论依据。     

Desmosomal gene evaluation in Boxers with arrhythmogenic right ventricular cardiomyopathy

OBJECTIVE: To sequence the exonic and splice site regions of the 4 desmosomal genes associated with the human form of familial arrhythmogenic right ventricular cardiomyopathy (ARVC) in Boxers with ARVC and identify a causative mutation. ANIMALS: 10 unrelated Boxers with ARVC and 2 unaffected Labrador Retrievers (control dogs). PROCEDURES: Exonic and splice site regions of the 4 genes encoding the desmosomal proteins plakophilin-2, plakoglobin, desmoplakin, and desmoglein-2 were sequenced. Sequences were compared for nucleotide sequence changes between affected dogs and the published sequences for clinically normal dogs and between affected dogs and the control dogs. Base-pair changes were considered to be causative for ARVC if they were detected in an affected dog but not in unaffected dogs, and if they involved a conserved amino acid and changed that amino acid to one of a different polarity, acid-base status, or structure. RESULTS: A causative mutation for ARVC in Boxers was not identified, although single nucleotide polymorphisms were detected in some affected dogs within exon 3 of the plakophilin-2 gene; exon 3 of the plakoglobin gene; exons 3 and 7 of the desmoglein-2 gene; and exons 6, 14, 15, and 24 of the desmoplakin gene. None of these changed the amino acid of the respective protein. CONCLUSIONS AND CLINICAL RELEVANCE: Mutations within the desmosomal genes associated with the development of ARVC in humans do not appear to be causative for ARVC in Boxers. Genomewide scanning for genetic loci of interest in dogs should be pursued.     

北京黑猪HoxB簇基因多态性与脊椎数及胴体性状的关联分析

旨在对北京黑猪HoxB簇9个基因(HoxB1-7、9和13)的多态性与脊椎数和胴体性状(胴体长、胴体直长、胴体斜长及胴体重)进行关联分析。本研究提取251头220日龄的健康北京黑猪耳组织DNA,对HoxB簇的9个基因通过引物设计、聚合酶链式反应(PCR)技术、Sanger测序技术等对SNPs进行基因分型，并计算变异位点基因型频率以及等位基因频率分布，并与脊椎数和胴体性状进行关联分析。结果，本试验共筛选到4个基因共12个非编码区的(UTR)SNPs,包括HoxB2基因的1个5′UTR突变、HoxB5基因的2个3′UTR突变、HoxB9基因的2个3′UTR突变以及HoxB13基因的7个3′UTR突变。将12个SNPs分别与脊椎数和胴体性状使用Duncan′s多重检验统计分析发现，HoxB2基因的1个5′UTR突变(c.40 C>T)、HoxB5基因的2个3′UTR突变(c.1766 A>G、c.1767 A>G)均与性状关联不显著(P>0.05);而HoxB9基因中的1个3′UTR突变(c.2743 C>T)与胴体性状关联显著(P<0.05),HoxB1...     

Understanding the use of Bayes factor for testing candidate genes

After quantitative trait loci (QTL) detection, one of the main objectives of research is to identify the causal mutation explaining phenotypic differences. Candidate genes are usually selected according to the physiological mechanism of the trait and their location within the same region of the QTL. After detection of any polymorphism at the candidate gene sequence, it is important to determine whether the detected mutation is the one that causes the phenotypic variation. This is not, however, an easy task, because of the linkage disequilibrium between the genes located in the same region. Several methods have been proposed that consider the neutral marker information in validating the involvement of candidate genes. However, some statistical information may be lost because of the presence of both the QTL and candidate gene effects in the model of analysis. Here, the Bayes factor is suggested as an alternative and a procedure for its calculation between candidate gene and QTL models is presented. The procedure is illustrated with a simulation study and with an example consisting of three SNPs detected at the leptin receptor (LEPR) in an experimental intercross between Iberian and Landrace pigs. The results indicate that the Bayes factor procedure is more powerful than the classical approach.     

Resistance to ETEC F4/F18–mediated piglet diarrhoea: opening the gene black box

Diarrhoea, a significant problem in pig rearing industry affecting pre- and post-weaning piglets is caused by enterotoxigenic Escherichia coli (ETEC). The ETEC are classified as per the fimbriae types which are responsible for bacterial attachment with enterocytes and release of toxins causing diarrhoea. However, genetic difference exists for susceptibility to ETEC infection in piglets. The different phenotypes found in pigs determine their (pigs’) susceptibility or resistance towards fimbrial subtypes/variants (F4ab, F4ac, F4ad and F18). Specific receptors are present on intestinal epithelium for attachment of these fimbriae, which do not express to same level in all animals. This differential expression is genetically determined and thus their genetic causes (may be putative candidate gene or mutations) render some animals resistant or susceptible to one or more fimbrial subtypes. Genetic linkage studies have revealed the mapping location of the receptor loci for the two most frequent variants F4ab and F4ac to SSC13q41 (i.e. q arm of 13th chromosome of Sus scrofa). Some SNPs have been identified in mucin gene family, transferring receptor gene, fucosyltransferase 1 gene and swine leucocyte antigen locus that are proposed to be linked mutations for resistance/susceptibility towards ETEC diarrhoea. However, owing to the variety of fimbrial types and subtypes, it would be difficult to identify a single causative mutation and the candidate loci may involve more number of genes/regions. In this review, we focus on the genetic mutations in genes involved in imparting resistance/susceptibility to F4 or F18 ETEC diarrhoea and possibilities to use them as marker for selection against susceptible animals.

     

Detection of occurrence of a recent genetic bottleneck event in Indian hill cattle breed Bargur using microsatellite markers

The effective number of breedable individuals is a crucial determinant for maintaining genetic variability within a population. The population of Bargur, the hill cattle of South India, has gone down drastically by more than 93 % in the past three decades, and only a few thousand animals are available at present. The present study was undertaken to evaluate Bargur cattle for mutation drift equilibrium and to detect the occurrence of recent genetic bottleneck event, if any, in this population. About 50 unrelated animals, true to the type, were sampled and genotyped at 25 microsatellite loci. The mean observed heterozygosity (0.808?±?0.023) was higher than the mean expected heterozygosity (0.762?±?0.008) with 15 out of 25 microsatellite loci exhibiting heterozygosity excess when assumed under Hardy–Weinberg equilibrium. To evaluate Bargur cattle for mutation drift equilibrium, three tests were performed under three different mutation models, viz., infinite allele model (IAM), stepwise mutation model (SMM) and two-phase model (TPM). The observed gene diversity (H _e) and expected equilibrium gene diversity (H _eq) were estimated under different models of microsatellite evolution. All the 25 loci were found to exhibit gene diversity excess under IAM and TPM, while 22 loci were having gene diversity excess under SMM. All the three statistical tests, viz., sign test, standardized differences test, and Wilcoxon sign rank test, revealed significant (P?<?0.01) deviation of Bargur cattle population from mutation-drift equilibrium under all the three models of mutation. Furthermore, the qualitative test of allele frequency distribution in Bargur cattle population revealed a strong mode shift from the normal L-shaped form suggesting that the population had experienced genetic bottleneck in the recent past. The occurrence of genetic bottleneck might have led to the loss of several rare alleles in the population, which point towards the need for efforts to conserve this important cattle germplasm. The present study is the first report in demonstrating the genetic basis of demographic bottleneck in an Indian cattle population.     

一种新的被毛突变小鼠遗传特性研究

对所发现的一种新的ＢＡＬＢ／ｃ突变小鼠的遗传特性，包括遗传规律、染色体组型和Ｇ带核型以及１９个生化基因部位进行了研究。该突变小鼠是由１对基因突变所致，该基因位于常染色体上，呈半显性遗传。３种表型小鼠的正常核型、Ｇ带核型以及所测定的所有生化基因部位间无明显差异，且与正常ＢＡＬＣ／ｃ小鼠的一致。     

Coat colour inheritance in horses

The colours of the horses have long been a subject of interest to owners and breeders of horses as well as to scientists. Though, the colour of horses has little to do with its performance, it is a primary means of identification and also the first indicator of questionable parentage. Probably the ancestral colour of the horse was a black-based pattern that provided camouflage protection against predators. Horse colours are mostly controlled by genes at 12 different loci. The three basic colours of horses are black, bay and chestnut. The genetic control of the basic colours of horses resides at two genetic loci, namely Extension (E) and Agouti (A) loci. Among the basic colours bay is dominant to black and both are epistatic to chestnut. Dilution of basic colours of horses as a result of four colour dilution genes such as cream dilution, dun, silver dapple and champagne resulted in extensive array of possible colours of horses. The most widespread and familiar of the horse colour dilution gene is the one that produces the golden body colour and are called as palomino or buckskin based on the colour of the points. The grey coat colour is due to the presence of dominant gene (G) at the grey locus. Grey is epistatic to all coat colour genes except white and a grey horse must have at least one grey parent. Roan is due to a dominant gene (Rn) at roan locus and this combines with any base colour to produce the various shades of roan pattern. White coat is due to a single dominant gene (W) and it is epistatic to the genes controlling all other colours. White marking in the face and legs are due to genetic and non-genetic factors. Several genes are involved in producing white markings. During recent years, comparative genomics and whole genome scanning have been used to develop DNA tests for different variety of horse colours. Molecular genetic studies on coat colour in horses helped in identification of the genes and mutation responsible for coat colour variants. In future, this will be applied to breeding programmes to reduce the incidence of diseases and to increase the efficiency of race horse population.     

鸡VLDLR基因多态性与蛋黄性状的关联分析

本研究采用PCR-RFLP方法,检测VLDLR基因在山东地方鸡种汶上芦花鸡、济宁百日鸡和莱芜黑鸡中的多态性,并分析各多态位点不同基因型与4个蛋黄性状的相关性。结果表明,在3个供试群体中共检测到2个具有生物学意义的SNPs位点,即第6外显子8 467nt处的G→A突变(V8467)和第17内含子13 876nt处的A→G突变(V13876)。最小二乘分析结果表明,V8467对蛋黄质量有极显著影响(P<0.01),对蛋黄高度有显著影响(P<0.05);V13876对蛋黄质量有极显著影响(P<0.01),对蛋黄比率和蛋黄高度有显著影响(P<0.05);而双倍型对蛋黄质量、蛋黄比率的影响均达到极显著水平(P<0.01),对蛋黄高度的影响达到显著水平(P<0.05)。结果提示:本研究检测到的VLDLR基因的V8467和V13876多态性位点可以作为蛋黄性状的候选分子标记。