Isolation of subtelomeric DNA sequences labelling sheep and goat chromosome ends

Two techniques that make it possible to isolate telomere DNA are presented, using sheep as an example. The first technique is based upon the screening of a sheep BAC library with PCR amplified DNA segments preserved from high-power laser beam irradiation. Twenty-three BACs hybridising to 13 subtelomeric regions in sheep and goats were obtained (out of 27 in the sheep complement), of which 13 recognised more than one region, telomeric or not. Twenty-three microsatellites were isolated from these BACs and 22 were genetically mapped on the sheep international genetic map, always consistently with the cytogenetical localisation in 17 cases out of 22. These results are discussed. The second technique is based upon the selective cloning of subtelomeric enriched DNA. Preliminary results were obtained by this approach.     

Hemoglobin function in the developing goat and sheep

Comparative studies of the blood of newly born goats and sheep have indicated a number of mechanisms which are responsible for a decreasing affinity for molecular oxygen in these developing animals during the first 40 to 60 days after birth.
The concentration of 2,3-DPG in the red cells of young goats increases four to sixfold during the first 3 to 4 days of life, and this increase is associated with a marked decrease in the cellular pH; 2,3-DPG does not bind to hemoglobins of goats and the decreased affinity for oxygen of goat blood at this period is apparently due to the lowered pH produced by the large increase of intracellular anions. Similar changes occur in young lambs.
After 15 to 20 days the changes of the dissociation curve are related more to structural differences between adult and fetal hemoglobins; cellular pH moves closer to the values of adult red cells. In goats of this age the predominate hemoglobins are those with β chains and these have dissociation curves shifted further to the right than other adult hemoglobins.
In young lambs Hb-C is found only in association with Hb-A but the amount present seldom exceeds 5 to 10%. The oxygen affinities of sheep Hb-A and Hb-C are identical but higher than that of sheep Hb-B.     

Relative DNA contents of somatic nuclei of ox,sheep and goat

Diploid ox nuclei contain about 14% more DNA than nuclei from sheep of the same sex. Goat nuclei have a similar DNA content to those of sheep. In view of the similar chromosome banding patterns in these species, it appears that chromosome evolution must have involved numerous minute interstitial deletions or additions of DNA. Although chromosomes which have similar banding patterns in these three species may be regarded as homologous in this respect, and can be regarded as having a common evolutionary origin, they are not homologous for the quantity of their DNA.     

DNA variants of the MHC show location-specific convergence between sheep, goat and cattle

Interspecific convergent evolution in sheep, goat and cattle was analysed with the help of orthologous microsatellite markers. Six of the loci are located in the major histocompatibility complex (MHC) region and three on different chromosomes. Samples from at least 60 animals per autochthonous breed of the three species were collected in central and southeast Anatolia (Turkey) as well as Baden-Württemberg (Germany). Allelic diversity, heterozygosity, population differentiation and genetic distances were calculated. The loci were polymorphic in all species and breeds. Apart from MSDRB, the loci linked to the MHC were similarly polymorphic as compared to the other loci. Allele numbers in the Turkish sheep and in the cattle breeds were higher than in the other breeds. The predominant occurrence of distinct allele lengths per locus differed depending on the species. For the three geographic locations, the genetic distances between species based on the MHC loci were significantly closer in comparison with distances based on quasi-neutral loci. This indicates convergent evolution of the MHC loci between sheep, goat and cattle caused by effects of location and demonstrates an approach for quantifying influences of adaptation on genetic variability.     

山羊、绵羊MT-Ⅳ分子特性研究

金属硫蛋白(MTs)是一类低分子量、金属和半胱氨酸含量高的细胞质蛋白, 哺乳动物的MTs包括MT-I、MT-II、MT-Ⅲ和MT-IV 4种亚型, 其中MT-IV只在磷状复层扁平上皮细胞中表达, 相关研究报道较少。本研究根据GenBank已公布的动物MT-IV基因序列, 设计出扩增山羊和绵羊MT-IV基因的特异性PCR引物MT-IVSP1和MT-IVSP2, 利用RT-PCR的方法, 分别从山羊和绵羊的瘤胃组织mRNA中, 克隆出山羊和绵羊的MT-IV基因编码区序列(均为189 bp), 序列登录GenBank, 获得序列号EF470251和EF624067。通过序列分析, 表明山羊和绵羊两个物种MT-IV基因编码区全编码均为189 bp、编码62个氨基酸, 其中绵羊的MT-IV含有20个半胱氨酸, 而山羊第61位保守的半胱氨酸被色氨酸所代替。两个物种的MT-IV均不含芳香族氨基酸, 含有MTs特有的C-X-C、C-X-X-C、C-C-X-C-C结构, 无明显的跨膜结构域, 无信号肽, 是一种细胞质蛋白。二级结构分析表明两个物种的MT-IV二级结构大多数为无规则卷曲结构, 分别在第7~9和第49~51氨基酸残基性存在折叠结构, 不存在螺旋结构。三级结构预测结果表明两个物种MT-IV的三级结构由a和b两个结构域组成, 其中β结构域相同, a结构域山羊少一个半胱氨酸残基, 其结构与绵间存在明显差异, 这一差异可能对山羊MT-IV的生理功能产生一定影响, 有必要深入研究。     

A comparative study of G+C-rich satellite components of sheep and goat DNA.

Restriction fragment patterns of G+C-rich satellites of sheep and goat DNA were compared. The 1,712 g/cm3 satellites of both species appear homologous, consisting of repeats 760 base pairs long and showing coincidence of position of primary+ EcoRI, BamHI and most BspRI restriction target sites. The EcoRI and BamHI endonucleases produce mostly monomers of the repeating unit, while oligomers prevail in the A1uI and Bg1II digests. Species-specific differences in the frequency, position and mode of distribution of secondary+ restriction target sites for EcoRI, Bg1II and A1uI were observed. Unlike the 1,712 g/cm3 satellites, the 1,723 g/cm3 component of sheep DNA and the 1,719 g/cm3 material from goat DNA appear species--specific, since no homologous material could ever be detected in the DNA of the other species.     

Current status of embryo technologies in sheep and goat

This review presents an overview of the technical bases of in vivo and in vitro embryo production in sheep and goat. The current limitations of in vivo production, such as variability of response to the hormonal treatment, fertilization failure in females showing a high ovulatory response, and the importance of premature regressed CL in the goat, are described along with possibilities for improvement. The new prospects offered by in vitro embryo production, by repeated ovum pick-up from live females and by juvenile breeding, are presented along with their limiting steps and research priorities. The recent improvements of embryo production and freezing technologies could be used for constitution of flocks without risks of disease transmission and will allow wider propagation of valuable genes in small ruminants populations in the future.     

A critical analysis of production-associated DNA polymorphisms in the genes of cattle, goat, sheep, and pig

Increasing productivity is one of the main objectives in animal production. Traditional breeding methods have led to increased gains in some traits but gains are not easily attainable in traits with low heritabilities. Exploiting the genetic variations underlying desired phenotypes is the goal of today's animal producers. Such positive genetic variants must, however, be known before possible application. Consequently, candidate genes of traits of interest have been searched for possible relationships with such traits or to explain reported quantitative trait loci (QTL) for such traits. DNA variants or polymorphisms have been identified in many such genes and their relationships with production traits determined. However, only a few genes have been evaluated, given the wealth of information on reported QTL for production traits, and in most cases genes are only partially investigated. This review presents available information on DNA variants for production traits and discusses steps that are required for effective utilization of this information for successful marker-assisted selection programs.     

A critical analysis of disease-associated DNA polymorphisms in the genes of cattle,goat, sheep,and pig

Genetic variations through their effects on gene expression and protein function underlie disease susceptibility in farm animal species. The variations are in the form of single nucleotide polymorphisms, deletions/insertions of nucleotides or whole genes, gene or whole chromosomal rearrangements, gene duplications, and copy number polymorphisms or variants. They exert varying degrees of effects on gene action, such as substitution of an amino acid for another, shift in reading frame and premature termination of translation, and complete deletion of entire exon(s) or gene(s) in diseased individuals. These factors influence gene function by affecting mRNA splicing pattern or by altering/eliminating protein function. Elucidating the genetic bases of diseases under the control of many genes is very challenging, and it is compounded by several factors, including host × pathogen × environment interactions. In this review, the genetic variations that underlie several diseases of livestock (under monogenic and polygenic control) are analyzed. Also, factors hampering research efforts toward identification of genetic influences on animal disease identification and control are highlighted. A better understanding of the factors analyzed could be better harnessed to effectively identify and control, genetically, livestock diseases. Finally, genetic control of animal diseases can reduce the costs associated with diseases, improve animal welfare, and provide healthy animal products to consumers, and should be given more attention.     

The economics of sheep and goat husbandry in Norse Greenland

Insight into the relative importance of sheep and goat herding and of the economic significance of each species (i.e., milk vs. meat vs. wool) in Medieval Greenland is obtained through the application of Halstead et al.'s (2002) criteria for the identification of adult ovicaprine mandibles to faunal assemblages from three Norse farmsteads: Sandnes, V52a, and ?71S. The economic strategies identified are broadly comparable between the two species and the Eastern and Western Settlement sites examined, and are suggestive of the subsistence production of meat and milk. Comparison with farmsteads elsewhere in Greenland indicates that socio-economic status and/or farmstead size interacted with geographical location in determining the economic strategies employed by the Norse farmers. A broader use of resources and a more varied diet are evident at larger farmsteads in Greenland and this paper suggests that such sites would have been better able than their smaller counterparts to withstand environmental deterioration during the early Middle Ages. These analyses have also confirmed that goats were relatively more common in Norse sites in Greenland than in Norse sites in Iceland, Orkney, or Shetland.     

25-Hydroxycholecalciferol levels in camel, sheep and goat.

1. The plasma levels of 25-hydroxycholecalciferol were measured in female dromedary camels, female sheep and Sinai desert goats. 2. The camels had levels of 443 +/- 96 ng/ml in summer, and 267 +/- 113 ng/ml in winter. 3. The sheep had levels of 40.7 +/- 9.09 ng/ml in summer and 37.1 +/- 8.82 ng/ml in winter, i.e. roughly the same as man in that region. 4. The goats had lower levels: 23.9 +/- 5.67 ng/ml in summer.     

Analysis of bovidae genomes: Arrangement of repeated and single copy DNA sequences in bovine,goat and sheep

Approximately 43–60% of the total genome in bovine, goat and sheep consisted of interspersed repeated and single copy DNA sequences. Most of the interspersed repeated DNA sequences were 1500–2400 nucleotide pair long while a minor portion was more than 4000 nucleotide pair long in goat and sheep and 3200 nucleotide pair long in bovine. About 1/3rd of single copy sequence were interspersed and their length was in the range of 1000–1500 nucleotide pairs.     

Restriction endonuclease analysis of mitochondrial DNA of three farm animal species: Cattle, sheep and goat

Five restriction endonucleases (HindIII, BgIII, EcoRI, EcoRV and BamHI) were employed to analyse mitochondrial DNA of cattle, sheep and goat. The results showed completely different restriction patterns of mtDNA among the three bovid species. A total of 11, 16, and 17 restriction fragments in cattle, sheep and goat respectively, were detected by the five restriction endonucleases. Average total sizes of mtDNA of cattle, sheep and goat were found to be 16.49 ± 0.18, 16.30 ± 0.25 and 16.44 ± 0.08 kb, respectively. The mtDNA cleavage patterns were identical for all seven individuals belonging to two cattle breeds and for 10 individuals from one sheep breed.