共查询到20条相似文献，搜索用时 15 毫秒
1.
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). 相似文献
2.
RUSSELL LB 《Science (New York, N.Y.)》1961,133(3467):1795-1803
3.
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. 相似文献
4.
5.
应用源自牛X和Y染色体同源区的1对外引物P1、P2及其各自特异区的2对内引物P3、P4和P5、P6,进行嵌套式PCR反应,对中国荷斯坦公、母牛静脉血样DNA及牛胚胎样DNA进行特异性条带的嵌套式PCR扩增,并对外、内嵌套式引物的PCR反应体系进行了优化,以准确鉴定牛早期胚胎性别.结果表明,在优化了的PCR反应体系下,中国荷斯坦公牛DNA样品得到178bp和262bp的两个条带,而母牛仅得到262bp的1个条带;静脉血样DNA性别鉴定结果与实际性别相符率为100%,表明本试验建立的体系完全可以用于牛早期的胚胎性别鉴定. 相似文献
6.
Polymorphic Y chromosomes harbor cryptic variation with manifold functional consequences 总被引：1，自引：0，他引：1
The paucity of polymorphisms in single-copy genes on the Y chromosome of Drosophila contrasts with data indicating that this chromosome has polymorphic phenotypic effects on sex ratio, temperature sensitivity, behavior, and fitness. We show that the Y chromosome of D. melanogaster harbors substantial genetic diversity in the form of polymorphisms for genetic elements that differentially affect the expression of hundreds of X-linked and autosomal genes. The affected genes are more highly expressed in males, more meagerly expressed in females, and more highly divergent between species. Functionally, they affect microtubule stability, lipid and mitochondrial metabolism, and the thermal sensitivity of spermatogenesis. Our findings provide a mechanism for adaptive phenotypic variation associated with the Y chromosome. 相似文献
7.
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 相似文献
8.
Rapid adaptive fixation of a new favorable mutation is expected to affect neighboring genes along the chromosome. Evolutionary theory predicts that the chromosomal region would show a reduced level of genetic variation and an excess of rare alleles. We have confirmed these predictions in a region of the X chromosome of Drosophila melanogaster that contains a newly evolved gene for a component of the sperm axoneme. In D. simulans, where the novel gene does not exist, the pattern of genetic variation is consistent with selection against recurrent deleterious mutations. These findings imply that the pattern of genetic variation along a chromosome may be useful for inferring its evolutionary history and for revealing regions in which recent adaptive fixations have taken place. 相似文献
9.
蒙古马染色体核型初步分析 总被引：3，自引：0，他引：3
本文采用外周血淋巴细胞短期培养方法,对蒙古马染色体进行了核型分析。分析结果表明,蒙古马的二倍体细胞染色体数为2n=64。其中有31对常染色体和1对性染色体(XY型)。31对常染色体中有13对为中部着丝点染色体和18对为端都着丝点染色体。X为近中着丝点染色体,Y为端部着丝点染色体。 相似文献
10.
为进一步优化橘小实蝇遗传性别品系大量饲养技术,对其性比与有效卵量的关系进行了研究.结果表明:在一定种群密度下,当性比(♀∶♂)为1∶2、1∶1、2∶1、4∶1时,单雌有效卵量间没有显著差异;对性比(X)和单雄有效卵量(Y)间的关系进行拟合,得到方程Y=0.747X3-36.408X2+887.368X-102.805,由方程可知,在一定种群密度下,1.5∶1♀∶♂2∶1的性比最适宜橘小实蝇遗传性别品系的人工繁育. 相似文献
11.
Gibbons A 《Science (New York, N.Y.)》2000,290(5494):1080-1081
Y chromosome data show that living Europeans have deep roots in the region--and researchers say genetic markers may be linked to cultures known from archaeological remains. In a report on page 1155, an international team reports that a wealth of data from the Y chromosome show that more than 80% of European men have inherited their Y chromosomes--which are transmitted only from father to son--from Paleolithic ancestors who lived 25,000 to 40,000 years ago. Thus, the genetic template for European men was set as early as 40,000 years ago, then modified--but not recast--by the Neolithic farmers who arrived in the region about 10,000 years ago. 相似文献
12.
Lush JL 《Journal of agricultural research》1925,30(10):893-913
The results of experiments carried out at the Wisconsin Agricultural Experiment Station to test the possibility of controlling sex by artificial insemination with centrifuged spermatozoa in rabbits and swine are presented. Microscopic studies of spermatozoa showed dimorphism in the head lengths but separation by centrifuging was not complete. According to the chromosome theory, if the ovum is fertilized by an X-bearing spermatozoon, the resulting individual will contain 2 X chromosomes in its cells and will be female. If the ovumn is fertilized by a Y-bearing chromoxome spermatozoon, the resulting individual will contain and X and a Y chromosome in its cells and be a male. The Y-containing spermatozoa are thought to have smaller heads than the X-containing ones. Centrifugal separation of male- and female-producing spermatozoa was attempted with liquid recovered by means of a catheter from the vagina and uterus of rabbits. Other rabbits were then artificially inseminated with portions of this liquid and sex of young produced was recorded. Many young were produced from centrifuged spermatozoa and many from spermatozoa exposed to low temperatures for periods up to 24 hours. Modification of sex ratios was not significant. This investigation failed to show a practical method of controlling sex ratios among the offspring of higher animals. 相似文献
13.
用外周血淋巴细胞培养方法研究了成都麻羊(Capra hircus)染色体的形态和数目,并进行G—带,C—带显带分析。结果是,正常麻羊染色体数目2n=60,29对常染色体皆为具近端着丝点染色体;公羊性染色体为XY,母羊为XX,其中Y染色体是染色体组中最小的,唯一具中间着丝点的染色体,X染色体是第三长的染色体。显带分析表明,每两条同源染色体具有相同的特定G—带带型,可与其它对染色体相区别,常染色体的着丝点区域G—带为浅染,性染色体则为深染。常染色的C—带位于端着丝点区域,X染色体则没有明显的C—带区。本文还对山羊,绵羊染色体组型进化的关系进行了探讨。 相似文献
14.
A human Y-linked DNA polymorphism and its potential for estimating genetic and evolutionary distance 总被引：29，自引：0，他引：29
M Casanova P Leroy C Boucekkine J Weissenbach C Bishop M Fellous M Purrello G Fiori M Siniscalco 《Science (New York, N.Y.)》1985,230(4732):1403-1406
A human DNA sequence (p12f2), derived from a partial Y-chromosome genomic library and showing homology with the X and Y chromosomes and with an undetermined number of autosomes, detected two Y-specific restriction fragment length variants on male DNA that had been digested with Taq I and Eco RI. These variants may have been generated through a deletion-insertion mechanism and their pattern of holoandric transmission indicates that they represent a two-allele Y-linked polymorphism (RFLP). By means of DNA from patients with inborn deletions in chromosome Y, this polymorphic DNA site was mapped to the interval Yq11.1-Yq11.22. The frequency of the rarest allele was about 35 percent in Algerian and Sardinian human males, whereas it was only 4 percent among Northern Europeans. The p12f2 probe also detected Y-specific DNA fragments in the gorilla and chimpanzee. In view of the monosomy of the Y chromosome in mammalian species, Y-linked RFLP's may prove to be more useful than autosomal or X-linked markers in estimating genetic distances within and between species. 相似文献
15.
关中马的染色体核型分析 总被引：3，自引：1，他引：3
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。 相似文献
16.
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 相似文献
17.
Instability of a 550-base pair DNA segment and abnormal methylation in fragile X syndrome 总被引：136，自引：0，他引：136
I Oberlé F Rousseau D Heitz C Kretz D Devys A Hanauer J Boué M F Bertheas J L Mandel 《Science (New York, N.Y.)》1991,252(5010):1097-1102
The fragile X syndrome, a common cause of inherited mental retardation, is characterized by an unusual mode of inheritance. Phenotypic expression has been linked to abnormal cytosine methylation of a single CpG island, at or very near the fragile site. Probes adjacent to this island detected very localized DNA rearrangements that constituted the fragile X mutations, and whose target was a 550-base pair GC-rich fragment. Normal transmitting males had a 150- to 400-base pair insertion that was inherited by their daughters either unchanged, or with small differences in size. Fragile X-positive individuals in the next generation had much larger fragments that differed among siblings and showed a generally heterogeneous pattern indicating somatic mutation. The mutated allele appeared unmethylated in normal transmitting males, methylated only on the inactive X chromosome in their daughters, and totally methylated in most fragile X males. However, some males had a mosaic pattern. Expression of the fragile X syndrome thus appears to result from a two-step mutation as well as a highly localized methylation. Carriers of the fragile X mutation can easily be detected regardless of sex or phenotypic expression, and rare apparent false negatives may result from genetic heterogeneity or misdiagnosis. 相似文献
18.
海门白山羊染色体核型研究及C-带分析 总被引：1，自引：0，他引：1
采用外周血淋巴细胞培养及染色体分带技术,分析了海门白山羊的染色体核型与C-带。结果表明,海门白山羊二倍体染色体数为2n=60,常染色体和X染色体均为端部着丝粒染色体,X染色体的大小介于1号和2号染色体之间,Y染色体最小,为中部着丝粒染色体,公羊核型为60,XY,母羊为60,XX。大部分常染色体和X,Y染色体着丝粒部位显示阳性C-带,但不同染色体的阳性C-带区域大小不同。 相似文献
19.
Percec I Plenge RM Nadeau JH Bartolomei MS Willard HF 《Science (New York, N.Y.)》2002,296(5570):1136-1139
X chromosome inactivation is the silencing mechanism eutherian mammals use to equalize the expression of X-linked genes between males and females early in embryonic development. In the mouse, genetic control of inactivation requires elements within the X inactivation center (Xic) on the X chromosome that influence the choice of which X chromosome is to be inactivated in individual cells. It has long been posited that unidentified autosomal factors are essential to the process. We have used chemical mutagenesis in the mouse to identify specific factors involved in X inactivation and report two genetically distinct autosomal mutations with dominant effects on X chromosome choice early in embryogenesis. 相似文献
20.
The signal for sex determination in the nematode Caenorhabditis elegans is the ratio of the number of X chromosomes to the number of sets of autosomes (X/A ratio). By previous genetic tests, elements that feminized chromosomal males appeared to be widespread on the X chromosome, but the nature of these elements was not determined. In experiments to define a feminizing element molecularly, cloned sequences were added to chromosomally male embryos by microinjection into the mother. Three different X-chromosome clones, including part of an actin gene, part of a myosin heavy chain gene, and all of two myosin light chain genes, feminize chromosomal males. Both somatic and germline aspects of sex determination are affected. In contrast, about 40 kilobases of nematode autosomal DNA, phage lambda DNA, and plasmid pBR322 DNA do not affect sex determination. A feminizing region was localized to a maximum of 131 base pairs within an intron of the X-linked actin gene; a part of the gene that does not have this region is not feminizing. The results suggest that short, discrete elements found associated with many X-linked genes may act as signals for sex determination in C. elegans. 相似文献