Effects of 5-azacytidine on lymphocyte-metaphases of Creole cows carrying the rob(1;29)

The Robertsonian translocation rob(1;29) is the most important chromosomal abnormality in cattle. It has been demonstrated that carriers of this chromosomal alteration exhibit reduced fertility due to an early embryonic loss. In the present study we analyzed the effects of DNA methylation inhibitor 5-azacytidine (5-aza-C) on metaphase lymphocytes from Uruguayan Creole cows carrying the rob(1;29). The analysis was focused on the chromatin structure of rob(1;29) comparing it to active and inactive BTAX chromosomes. Lymphocyte cultures were treated with 5-aza-C (1 × 10⁻³ M) for 2 h to analyze regions of chromatin decondensation. A comparative analysis of chromatin decondensation among rob(1;29), active BTAX and inactive BTAX showed significant differences (p = 1.07 × 10⁻⁷). Post-hoc pair-wise comparisons using the Mann-Whitney U-test showed significant differences between rob(1;29) and active BTAX (p = 1.97 × 10⁻⁵) and between the active BTAX and inactive BTAX (p = 2.55 × 10⁻⁷). Nevertheless, rob(1;29) did not show significant differences when compared to inactive BTAX (p = 0.078). Robertsonian translocation rob(1;29) showed a despiralization pattern similar to the inactive X chromosome. Pericentromeric despiralization in rob(1;29) and the inactive X chromosome was similar, with an average value and standard error of 0.75 ± 0.11 and 0.75 ± 0.083, respectively. A single condensed region was observed in the inactive X chromosome, whereas in rob(1;29) two regions of condensation, one proximal to the centromere and another proximal to the telomere were detected. Our results show that rob(1;29) and the inactive X chromosome present instability regions susceptible to 5-aza-C. Further studies will be needed to understand the nature and expression pattern of genes located in chromatin condensed regions of rob(1;29).     

Use of molecular markers for the identification of River Buffalo chromosomes: chromosome one

A standard karyotype for the River Buffalo has recently been established. The largest five chromosomes are biarmed and, based on the banding homology between cattle and buffalo chromosomes, were suggested to originate from the fusion of cattle acrocentric chromosomes. The origin of buffalo chromosome 1 is controversial due to the difficulty in differentiating between the small acrocentric cattle chromosomes. Using molecular markers assigned to cattle chromosomes, synteny between CD18, a marker for BTA1, and markers for small acrocentric cattle chromosomes BTA 24 to BTA 29 was investigated in buffalo/hamster somatic cell hybrids. The investigation revealed that CD18 is syntenic with ANT1, a marker for cattle chromosome 27. The present results confirm that buffalo BBU1 results from fusion of cattle BTA 1 and BTA 27. They also underline the importance of biarmed buffalo chromosomes for the identification of small cattle acrocentrics.     

Reciprocal translocations in cattle: frequency estimation

Chromosomal anomalies, like Robertsonian and reciprocal translocations, represent a big problem in cattle breeding as their presence induces, in the carrier subjects, a well‐documented fertility reduction. In cattle, reciprocal translocations (RCPs, a chromosome abnormality caused by an exchange of material between non‐homologous chromosomes) are considered rare as to date only 19 reciprocal translocations have been described. In cattle, it is common knowledge that the Robertsonian translocations represent the most common cytogenetic anomalies, and this is probably due to the existence of the endemic 1;29 Robertsonian translocation. However, these considerations are based on data obtained using techniques that are unable to identify all reciprocal translocations, and thus, their frequency is clearly underestimated. The purpose of this work is to provide a first realistic estimate of the impact of RCPs in the cattle population studied, trying to eliminate the factors that have caused an underestimation of their frequency so far. We performed this work using a mathematical as well as a simulation approach and, as biological data, we considered the cytogenetic results obtained in the last 15 years. The results obtained show that only 16% of reciprocal translocations can be detected using simple Giemsa techniques, and consequently, they could be present in no <0.14% of cattle subjects, a frequency five times higher than that shown by de novo Robertsonian translocations. This data is useful to open a debate about the need to introduce a more efficient method to identify RCP in cattle.     

1/25 translocations in Blonde d'Aquitaine cattle in New Zealand

A Robertsonian centric fusion between chromosomes 1 and 25 in Blonde d'Aquitaine cattle in New Zealand is reported. This fused chromosome is the same as the widely reported 1/29 translocation chromosome with the difference in the numbering arising from inconsistencies in the G and R-banded cattle karyotypes of the International System for Cytogenetic Nomenclature of Domestic Animals, 1989.     

Presumptive 1/29 autosomal translocation in Australian cattle.

A cytogenetical study was made of 9 descendants of a Charolais bull, heterozygous for a presumptive 1/29 translocation, three of the dams of some of these descendants, and three unrelated bulls which were mated to some of the descendants. Photographic karyotypes of Giemsa stained and C-banded chromosomes were prepared for each animal. The dams of the progeny showed no chromosomal abnormalities indicating that translocations were inherited from the sire. Three daughters of the Charolais bull and two of his grand daughters were heterozygous for the translocation, with a modal chromosomal number of 59, while the remaining three daughters and their progeny possessed normal karyotypes. No phenotypic abnormalities were observed in the animals examined. Measurements of the arms of the chromosomes suggested that the translocation chromosome (a large submetacentric) contained chromosomes 1 and 29. The submetacentric translocation chromosome had a single C-band, the two submetacentric X chromosomes showed no C-bands and each acrocentric autosome had a single C-band. All cattle heterozygous for the translocation showed normal fertility.     

布尔山羊的染色体核型分析

采用外周血淋巴细胞培养法，对布尔山羊的染色体核型进行了分析。结果表明，布尔山羊的二倍体染色体数目为2n=60，公羊核型为60，XY；母羊核型为60，XX。共有29对常染色体和1对性染色体。所有常染色体均为端部着丝点染色体；X染色体为第二大的端部着丝点染色体，Y染色体为最小的天是唯一的中部着丝点染色体。研究发现，布尔山羊存在1.7％的三倍体和5.9％的四倍体。     

牛亚科物种TRs分布特点及着丝粒区卫星DNA进化研究

旨在研究牛亚科物种间串联重复序列（tandem repeats sequence,TRs）的分布特点及着丝粒区卫星DNA的进化关系。本研究基于普通牛、瘤牛、牦牛、水牛、野牛、独龙牛6个牛亚科物种的基因组序列,研究了不同物种间TRs的组成、分布及结构特点,并分析了6个牛亚科物种染色体着丝粒区卫星DNA的进化关系。结果表明：1）TRs在牛亚科物种中平均占比为2.03%,平均长度54.93 Mb,其中普通牛的占比最高3.42%（93.00 Mb）,瘤牛最低1.42%（37.88 Mb）。2）微卫星DNA在3类TRs中位点数最多,为483 405,占TRs总位点数85.64%,高于小卫星DNA（43 026,7.62%）和卫星DNA（38 180,6.75%）。3）通过对微卫星DNA丰度和平均长度分析发现,二碱基微卫星DNA在牛亚科物种中丰度最高,为70.93 loci/Mb,且以AC拷贝类别为主。4）通过构建着丝粒区1.715和1.723卫星DNA的系统发育树发现,1.715卫星DNA普遍存在于牛亚科物种的基因组中,而1.723卫星DNA在牦牛中不存在,两类卫星DNA在不同物种间或不同染色体上存在不同程度分化,具有较明显的种间特异性。TRs在牛亚科6个物种中平均占比为2.03%,微卫星DNA为TRs主要序列,且二碱基微卫星丰度最高,并以AC拷贝类别为主;1.715卫星DNA普遍存在于6个牛亚科物种的基因组中,但在物种间或染色体间存在不同程度分化。本研究结果为牛亚科物种间TRs分布特征及进化关系研究提供了重要理论依据。     

猪13/17罗伯逊易位染色体的显微分离及DOP-PCR扩增

以13／17罗伯逊易位杂合子猪[2n=37，XY或XX，rob（13：17）]为材料，制备其有丝分裂中期染色体，利用显微分离技术对13／17罗伯逊易位染色体进行分离，并将单条染色体进行简并寡核苷酸引物PCR（degenerate oligonucleotide primer-PCR．DOP-PCR）扩增，其扩增片段大小主要在0．2～2．5kb之间；以DOP-PCR扩增产物为模板，分别以猪13、17号染色体近着丝点微卫星标记S0282和SW335为扩增目的基因，对D0P-PCR扩增产物进行鉴定，结果表明DOP-PCR产物来源于13／17罗伯逊易位染色体。该方法的成功建立为进一步从分子水平上研究家猪13／17罗伯逊易位所引起的表型效应的遗传机制以及筛选猪13和17号染色体上新的分子遗传标记奠定了基础。     

13/17染色体易位纯合子猪(2n=36)与正常核型家猪(2n=38)的杂交试验

用13/17染色体易位杂合子猪互交获得的1头13/17染色体易位纯合子公猪[2n=36,XY,rob(13/17)]与4头正常核型母猪(2n=38,XX)交配,结果4头母猪全部妊娠并正常分娩.其产仔数分别为13,16,12,11,产活仔数分别为12,13,12,11;窝断奶头数分别为12,13,9,10.经核型鉴定,其后代全部为13/17易位杂合子[2n=37,XX或XY,rob(13/17)].此结果表明,13/17易位染色体的遗传完全符合孟德尔的遗传规律,13/17易位纯合子公猪具有正常的繁殖力.本杂交试验所产活仔48头,其性别比例为35?:13?,接近3:1的比例,经X~2检验不符合1:1的理论比率(X~2=10.08,P<0.01).此外,本杂交试验所产仔猪生长发育正常,并具有一定的杂合优势,这一结果为13/17易位纯合子猪的进一步推广应用,尤其是作为商品猪生产的杂交父本提供了可靠依据.     

猪单条13/17罗伯逊易位染色体的显微分离与LA-PCR扩增

以13/17罗伯逊易位纯合子猪［2n=36，XY或XX，rob(13;17)］为试验材料，制备其有丝分裂中期染色体，利用显微分离技术对13/17罗伯逊易位染色体进行分离，并将单条染色体进行LA-PCR扩增，其扩增片段大小主要在200~2800 bp；对LA-PCR扩增产物用猪13、17号染色体近着丝点微卫星标记SWR1941和SWR1120与Southern杂交2种方法进行鉴定，结果表明LA-PCR产物来源于13/17罗伯逊易位染色体。该方法的成功建立为进一步从分子水平上研究家猪13/17罗伯逊易位所引起的表型效应的遗传机制以及筛选猪13和17号染色体上新的分子遗传标记奠定了基础。     

Y CHROMOSOME MORPHOLOGY OF CATTLE

Metaphase chromosomes from cultured lymphocytes were prepared from 246 bulls including Bos indicus, Bos taurus. Bos (Bibos) banteng, Sanga and interspecific and intra-specific breed crosses. Morphology and karyotype position of the Y chromosome for each bull were noted. Karyotype position of the Y chromosome varied between bulls from 25th to 29th pair and the Y chromosomes of Bos indicus and breeds derived from Bos indicus bulls were acrocentric while those of Bos taurus, Sanga and breeds derived from these bulls were metacentric/submetacentric. Two forms of Y chromosome were noted in the Droughtmaster breed. C-banding patterns of the acrocentric Y chromosome were characteristic and enabled easy identification.     

种公牛1/29染色体罗伯逊易位的检测结果及其遗传效应分析

通过对夏洛来、利木赞、西门塔尔三个品种共98头种公牛染色体的遗传检测，在加系夏洛来牛中发现一例1／29染色体罗伯逊易位纯合种公牛及后代1／29罗伯逊易位杂合母牛一例。讨论了1／29染色体罗伯逊易位对繁殖性能的影响。三品种种公牛Y染色体均为中部着丝点，X染色体有中部着丝点和亚中部着丝点两种类型，在品种间呈多态性。     

鉴别牛早期胚胎性别PCR方法引物的设计与筛选

根据牛Y-染色体特异重复序列、睾丸特异蛋白基因以及性别决定基因序列设计合成5对公牛Y-染色体特异引物，依据牛骨胳肌α肌动蛋白前体基因和微卫星DNA序列设计合成4对牛DNA特异引物(内标引物)。单重PcR扩增牛基因组DNA，筛选出4对牛Y-染色体特异引物和1对牛DNA特异内标引物。将不同的Y-染色体特异引物与内标引物组合，多重PCR扩增牛基因组DNA、已知性别的牛成纤维细胞和克隆胚胎，筛选出2个可用于牛早期胚胎性别鉴别的PCR引物组合：B34／A12和B78／A12。     

Detection of quantitative trait loci for growth and carcass composition in cattle

The objective of the present study was to detect quantitative trait loci for economically important traits in a family from a Bos indicus x Bos taurus sire. A Brahman x Hereford sire was used to develop a half-sib family (n = 547). The sire was mated to Bos taurus cows. Traits analyzed were birth (kg) and weaning weights (kg); hot carcass weight (kg); marbling score; longissimus area (cm2); USDA yield grade; estimated kidney, pelvic, and heart fat (%); fat thickness (cm); fat yield (%); and retail product yield (%). Meat tenderness was measured as Warner-Bratzler shear force (kg) at 3 and 14 d postmortem. Two hundred and thirty-eight markers were genotyped in 185 offspring. One hundred and thirty markers were used to genotype the remaining 362 offspring. A total of 312 markers were used in the final analysis. Seventy-four markers were common to both groups. Significant QTL (expected number of false-positives < 0.05) were observed for birth weight and longissimus area on chromosome 5, for longissimus area on chromosome 6, for retail product yield on chromosome 9, for birth weight on chromosome 21, and for marbling score on chromosome 23. Evidence suggesting (expected number of false-positives < 1) the presence of QTL was detected for several traits. Putative QTL for birth weight were detected on chromosomes 1, 2, and 3, and for weaning weight on chromosome 29. For hot carcass weight, QTL were detected on chromosomes 10, 18, and 29. Four QTL for yield grade were identified on chromosomes 2, 11, 14, and 19. Three QTL for fat thickness were detected on chromosomes 2, 3, 7, and 14. For marbling score, QTL were identified on chromosomes 3, 10, 14, and 27. Four QTL were identified for retail product yield on chromosomes 12, 18, 19, and 29. A QTL for estimated kidney, pelvic, and heart fat was detected on chromosome 15, and a QTL for meat tenderness measured as Warner-Bratzler shear force at 3 d postmortem was identified on chromosome 20. Two QTL were detected for meat tenderness measured as Warner-Bratzler shear force at 14 d postmortem on chromosomes 20 and 29. These results present a complete scan in all available progeny in this family. Regions underlying QTL need to be assessed in other populations.     

C- AND G- BANDING PATTERNS AND CHROMOSOMAL MORPHOLOGY OF SOME BREEDS OF AUSTRALIAN CATTLE

A cytogenetical study using metaphase chromosomes from cultured lymphocytes, was made of 2 Banteng (Bibos banteng) steers and 218 bulls representing 13 purebreeds (Bos taurus type, Bos indicus type and Sanga) and 7 cross-breeds. Studies were made of photographic karyotypes of Giemsa stained and C-banded chromosomes of bulls of each breed and of B-banded chromosomes from 3 breeds of Bos indicus and one cross-breed Australian Friesian Sahiwal) cattle. The relative lengths of chromosomes of Bos taurus and Bos indicus bulls were compared and significant difference in relative lengths of the X chromosomes were noted between these two species. There was a differences in morphology of the Y chromosomes; Sanga, Banteng and Bos taurus type breeds had a small submetacentric Y chromosome, except for the Jersey which had a metacentric Y chromosome. All Bos indicus type bulls had an acrocentric Y chromosome but the Droughtmaster breed had two forms of the Y chromosome (submetacentric and acrocentric). The C-banding patterns of the autosomes and X chromosomes were similar for all breeds while those of the Y chromosomes of Bos indicus type cattle allowed their accurate identification. G-banding patterns of Bos indicus resembled those of Bos taurus and enabled pairing of homologous chromosomes. Centromeres of the autosomes were unstained but those of the sex chromosomes were darkly stained.     

科尔沁牛染色体14/24易位的初步研究

对内蒙古哲盟地区的5头科尔沁牛进行了细胞遗传学检查。结果:3♀和1♂核型全为2n=60,可配成30对,29对常染色体和1对性染色体,性染色体X为大型亚中着丝粒,Y为小型亚中着丝粒染色体;1♂的核型为异常核型,59,XY,t(14:24)。14/24易位是单独发生的。     

青海四种土蝗(直翅目:斑翅蝗科)染色体核型分析

用常规染色体制片方法研究了青海高山草地的四种土蝗：黄胫异痂蝗（Bryodemella bolderei holdereri Krauss,)、白边痂蝗（Bryodema luctuosum luctuosun Stoll)，黄胫小车蝗（Oedaleus infernalis Sauss）、亚洲小车蝗（Oedaleu asiatisc B.-Bienko）的染色体数目和核型。四种土蝗染色体数目均为，（2n♂）＝23＝27＝22＋XO；全部染色体都为近端着丝点类型；四种土蝗染色体的核型公式均为K(2n,♂）＝23＝23T＝4L＋14M＋4S＋XO。结果表明，斑翅蝗科3属间的蝗虫主要区别为常染色体和性染色体相对长度有明显差异，小车蝗属内2种间区别主要为常染色体相对长度的差异。     

Centric fusion translocations in cattle: a review

The incidence of centric fusion (Robertsonian) translocation in cattle breeds is reviewed. Thirteen different centric fusions have been identified in cattle, with few breeds carrying more than one translocation. Of the commercial breeds, Friesian-Holstein cattle appear to be free of translocations, while the Simmental is the only one which carries three translocations. The major effect of centric fusion is on fertility, causing unbalanced gametes and hence unbalanced zygotes to be formed, leading to early embryonic death. However, to discard all translocation-carrying animals may be misguided as they represent genetic variation and a source of desirable traits.     

藏獒染色体核型分析

采用外周血淋巴细胞培养法和常规染色体分析技术,对青海省藏獒的染色体核型进行了分析。结果表明：藏獒二倍体染色体数目为2n=78,NF=80,按形态可分为39对,除性染色体X和Y为中着丝粒（M）染色体外,其它38对常染色体均为端着丝粒（T）染色体。     

Trisomy 2 in three cases of canine haemangiopericytoma.

Two female (12 and 14 years old) and one male dog (10 years old) developed haemangiopericytomas. Three copies of chromosome 2 were present in the tumours of all three dogs. Additional alterations were an interstitially deleted chromosome 1, centric fusions 3/34 and 8/15, isochromosome 32 and two unidentified marker chromosomes (M1, M2) in one bitch. In the other bitch, the additional alterations were trisomy 37, centric fusions 8/38 and 30/31, and a derivative chromosome 13 (der13). In the male dog, tandem fusion 2/19 was present in addition to two structurally normal chromosomes 2.