X-Chromosome inactivation in cloned mouse embryos

To study whether cloning resets the epigenetic differences between the two X chromosomes of a somatic female nucleus, we monitored X inactivation in cloned mouse embryos. Both X chromosomes were active during cleavage of cloned embryos, followed by random X inactivation in the embryo proper. In the trophectoderm (TE), X inactivation was nonrandom with the inactivated X of the somatic donor being chosen for inactivation. When female embryonic stem cells with two active X chromosomes were used as donors, random X inactivation was seen in the TE and embryo. These results demonstrate that epigenetic marks can be removed and reestablished on either X chromosome during cloning. Our results also suggest that the epigenetic marks imposed on the X chromosomes during gametogenesis, responsible for normal imprinted X inactivation in the TE, are functionally equivalent to the marks imposed on the chromosomes during somatic X inactivation.     

拟水狼蛛染色体的初步观察

以附肢形成之前的蜘蛛胚胎细胞为材料,经秋水仙素处理、纸渗、固定、制片及染色,对拟水狼蛛的体细胞染色体进行了初步观察．结果表明：拟水狼蛛的染色体数为：雄性２ｎ＝２６,雌性２ｎ＝２８,性别决定机制为Ｘ１Ｘ２Ｏ．Ｃ－带分析表明,所有染色体都为端着丝粒染色体,端部有特异性染色质存在．     

甘肃白猪性畸形及其对生产性能的影响

为了配合育种工作,作者采用常规染色体制备方法,对96头甘肃白猪及其杂交猪的染色体作了研究。检出核型为38,XY的雌性个体2头。染色体G—带和性染色质分析的结果表明它们具有1条Y染色体和1条X染色体。对这2头间性个体的肥育性能、胴体成绩和肉品质三项指标测定结果表明,间性个体与正常个体无显著差异。由于这2头个体均与武武品系有关,所以在这一品系的选育中应给予高度重视。     

Molecular analysis of a constitutional X-autosome translocation in a female with muscular dystrophy

The gene responsible for Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) maps to the X chromosome short arm, band Xp21. In a few females with DMD or BMD, the Xp21 region is disrupted by an X-autosome translocation. Accumulating evidence suggests that the exchange has physically disrupted the DMD/BMD locus to cause the disease. One affected female with a t(X;21)(p21;p12) translocation was studied in detail. The exchange points from both translocation chromosomes were cloned, restriction-mapped, and sequenced. The translocation is reciprocal, but not conservative. A small amount of DNA is missing from the translocated chromosomes; 71 to 72 base pairs from the X chromosome and 16 to 23 base pairs from the 28S ribosomal gene on chromosome 21.     

Chromosomal aberrations in a population of ground squirrels

Chromosomes were analyzed from a population of Spermophilus beldingi that included an adult female and three juveniles from the same burrow. All animals had a diploid number of 30. The adult and a juvenile female from the burrow had identical aberrant karyotypes containing an unpaired submetacentric and a minute metacentric chromosome. A familial aberration involving an X chromosome, without phenotypic alteration, is most probable.     

Adenosine triphosphate: protection against radiation-indued chromosome loss in Drosophila

Injection of 5 milligrams of adenosine triphosphate per milliliter into adult Drosophila melanogaster X(e2) yB/sc(8) y(+) 4 to 8 hours old either immediately before or after administration of 2000 roentgens of x-rays protected those cells in spermatogenesis which were in or near meiosis from the loss of the ring X or the y(+) portion of Y chromosome. The loss of the chromosomes was determined by appearance of exceptional XO males in the offspring.     

黄鳝体内新棘衣棘头虫染色体核型及G带分析

采用空气干燥和胰酶消化法,对黄鳝体内新棘衣棘头虫[Pallisentis(Neosentis)celatus]的染色体核型和G-带进行研究,结果表明,新棘衣棘头虫由3对常染色体和1对性染色体组成,其中X染色体和1号、3号都为中着丝粒染色体,2号为亚中着丝粒染色体,Y为端着丝粒染色体,核型公式为2n=5m+2sm+1t;性别决定模式为XX-XY;每对染色体都有特定的G-带带型.     

Polycomb proteins targeted by a short repeat RNA to the mouse X chromosome

To equalize X-chromosome dosages between the sexes, the female mammal inactivates one of her two X chromosomes. X-chromosome inactivation (XCI) is initiated by expression of Xist, a 17-kb noncoding RNA (ncRNA) that accumulates on the X in cis. Because interacting factors have not been isolated, the mechanism by which Xist induces silencing remains unknown. We discovered a 1.6-kilobase ncRNA (RepA) within Xist and identified the Polycomb complex, PRC2, as its direct target. PRC2 is initially recruited to the X by RepA RNA, with Ezh2 serving as the RNA binding subunit. The antisense Tsix RNA inhibits this interaction. RepA depletion abolishes full-length Xist induction and trimethylation on lysine 27 of histone H3 of the X. Likewise, PRC2 deficiency compromises Xist up-regulation. Therefore, RepA, together with PRC2, is required for the initiation and spread of XCI. We conclude that a ncRNA cofactor recruits Polycomb complexes to their target locus.     

关中马的染色体核型分析

采用外周血淋巴细胞培养法 ,对关中马的染色体核型进行了研究。结果表明 ,关中马的二倍体染色体数目为 2 n=6 4,公马核型为 6 4,XY;母马核型为 6 4,XX,包括 31对常染色体和 1对性染色体。 31对常染色体中 ,13对为中部或亚中部着丝点染色体 ,18对为端部着丝点染色体 ;1对性染色体中 ,X染色体为 1条第二大的亚中部着丝点染色体 ,Y染色体为最小的端部着丝点染色体。     

Regulation of the different chromatin states of autosomes and X chromosomes in the germ line of C. elegans

The Maternal-Effect Sterile (MES) proteins are essential for germline viability in Caenorhabditis elegans. Here, we report that MES-4, a SET-domain protein, binds to the autosomes but not to the X chromosomes. MES-2, MES-3, and MES-6 are required to exclude MES-4 and markers of active chromatin from the X chromosomes. These findings strengthen the emerging view that in the C. elegans germ line, the X chromosomes differ in chromatin state from the autosomes and are generally silenced. We propose that all four MES proteins participate in X-chromosome silencing, and that the role of MES-4 is to exclude repressors from the autosomes, thus enabling efficient repression of the Xs.     

山羊与绵羊的染色体核型比较

采用外周血淋巴细胞培养法 ,对关中奶山羊和同羊的染色体核型进行分析。结果表明 ,关中奶山羊染色体数 2 n=60 ,其中有 2 9对常染色体和 1对性染色体 ,常染色体都为端部着丝点染色体。X染色体为第二对最大的端部着丝点染色体 ,Y染色体为唯一的、最小的中部着丝点染色体。同羊二倍体染色体数 2 n=5 4,其中包括 2 6对常染色体和 1对性染色体 ,常染色体中有 3对为中着丝点染色体 ,2 3对为端着丝点染色体 ,X染色体为最大的近端着丝点染色体 ,Y染色体为最小的亚中着丝点染色体     

微尾鼩种群数量变动及其预测

根据南充市防疫站1976-2002年和廖文波等2003年9月-2004年8月的鼠形小兽的调查和监测资料,对该地区优势种群微尾鼩(Anourosorexsquamipes)种群数量变动及预测进行了分析。6个时期内微尾鼩种群数量变化在室内生境不具有周期性(s<0.5);室外生境具周期性(s> 0. 5); 1a有6月和11 -12月2次数量高峰,未成年组(Ⅰ)微尾鼩相对密度冬季最高,春季最低,成年Ⅱ组(Ⅲ)夏季最高,冬季最低;利用回归分析法建立了微尾鼩种群成亚比、雌性成亚比和雄性成亚比提前2个月预测种群密度的3个回归方程:Y=0.167X-4.065;Y=0.148X-2.754;Y=0.142X-1.830,发现种群密度的预测值与实测值基本吻合。     

3个黄牛品种染色体的G带模式图研究

对秦川牛、岭南牛、西镇牛的染色体进行了 G带研究 ,结果表明 ,这 3个黄牛品种除 Y染色体以外的所有染色体对 ,其 G带带型基本一致。每对染色体都有其独有的带纹特征 ,可用于识别牛的每条染色体。Y染色体有中部 (或亚中部 )和近端着丝粒染色体。根据 3个黄牛品种 G带带型的共同特点 ,对其染色体带型进行了描述、分区和命名 ,并绘制了牛 86个区 354条带的 G带模式图     

青山羊染色体G—带型研究

本文采用外周血淋巴细胞培养技术,分析了青山羊染色体核型和 G—带带型,结果是:青山羊二倍体染色体2n=60,常染色体全部为端着丝粒染色体,X 染色体为第三号,是端着丝粒染色体,Y 染色体最小,是中部着丝粒染色体,用胰酶吉姆萨带显示青山羊 G—带型,并绘制了青山羊中期染色体 G—带模式图。     

青杨脊虎天牛对伴生真菌的触角电位反应

为了探索伴生真菌在青杨脊虎天牛寄主选择过程中的作用,利用触角电位法(EAG)测试了青杨脊虎天牛对伴生的46株真菌的触角电位反应。结果表明:有11个菌株能够引起青杨脊虎天牛雌成虫明显的EAG反应,其中6个菌株与对照相比差异极显著;雌成虫对2株腐皮镰刀菌(Fusarium solani(Mart.)Sacc.)具有较强的EAG反应,EAG最高相对均值达201.67%和199.00%,约为对照的2倍,差异极显著;有17个菌株能够引起青杨脊虎天牛雄成虫明显的触角电位反应,其中3个菌株与对照相比差异极显著。     

Chromosome Changes Induced by Infections in Tissues of Rhynchosciara angelae

The main effects of two infections, one by a protozoan and the other by a virus, in cells of Rhynchosciara angelae (Diptera, Sciaridae) are an increase in cell size and changes in the size, shape, and behavior of the chromosomes. The X chromosome of some cells reacts differently from the autosome to the protozoan infection. Some chromosomes show specific, easily traceable points after infection by the virus. Some of the effects of these infections may be similar to the effects of infective agents in other organisms.     

Epigenetic aspects of X-chromosome dosage compensation

The X chromosomes of mammals and fruit flies exhibit unusual properties that have evolved to deal with the different dosages of X-linked genes in males (XY) and females (XX). The X chromosome dosage-compensation mechanisms discovered in these species are evolutionarily unrelated, but exhibit surprising parallels in their regulatory strategies. These features include the importance of noncoding RNAs, and epigenetic spreading of chromatin-modifying activities. Sex chromosomes have posed a fascinating puzzle for biologists. The dissimilar organization, gene content, and regulation of the X and Y chromosomes are thought to reflect selective forces acting on original pairs of identical chromosomes (1-3). The result in many organisms is a male-specific Y chromosome that has lost most of its original genetic content, and a difference in dosage of the X chromosome in males (XY) and females (XX).     

Maintenance of normal in situ chromosomal features in long-term tissue cultures

Clonal isolates from a rapidly proliferating fibroblast-like derivative have retained the classic diploid chromosome relationship over a period of many transplant generations. The readily identified members of the 11 pairs of chromosomes, including the sex chromosomes (X(1) and X(2)), have aided in localizing minute structural alterations within recloned diploid and aneuploid sublines.