首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   26篇
  完全免费   5篇
  1996年   1篇
  1992年   1篇
  1991年   3篇
  1989年   1篇
  1986年   2篇
  1985年   1篇
  1984年   2篇
  1983年   1篇
  1982年   1篇
  1980年   5篇
  1979年   1篇
  1978年   1篇
  1977年   4篇
  1976年   1篇
  1975年   2篇
  1974年   1篇
  1973年   3篇
排序方式: 共有31条查询结果,搜索用时 125 毫秒
1.
A human X-Y homologous region encodes "amelogenin"   总被引:21,自引:0,他引:21  
Results of cloning and sequencing of genomic sequences from the X and Y chromosomes that encode the tooth enamel gene amelogenin (both AMG and AMGL) are described. Three exons are defined on both the X and Y sequences. The nucleotide sequences reported here offer basic information for investigating human amelogenin.  相似文献
2.
We have determined the complete nucleotide sequence of a 3564 bp EcoRI fragment which represents a major component of the human Y-chromosome specific repeated DNA family (DYZ1). Sequencing result showed a tandem array of pentanucleotides after five nucleotides were inserted or deleted at four positions. 229 out of the 713 pentanucleotides were TTCCA, and 297 were its single-base substituents. Southern hybridization analyses of male genomic DNAs showed that several endonuclease cleavage sites were located at intervals of 3.56kb in the DYZ1 locus. This indicates that the DYZ1 repeated DNA family evolved and expanded by unequal crossovers which occurred at distances of 3.56kb. As there is a uniformly distributed array of pentanucleotides on this locus, it is not a sequence homology that determines the distance of unequal crossovers. A higher order of chromatin structure may be involved in the determination of distance in unequal crossovers.  相似文献
3.
Amelogenesis imperfecta is characterized by the defective formation of tooth enamel. Here we present evidence that the X-linked form of this disorder (AIH1) is caused by a structural alteration in one of the predominant proteins in enamel, amelogenin. Southern blot analysis revealed a deletion extending over 5 kb of the amelogenin gene in males with the hypomineralization form of the AIH1. Carrier females were heterozygous for the molecular defect. The deletion appears to include at least two exons of the amelogenin gene and the extent of the deletion was verified by PCR analysis. The mutation was shown to segregate with the disease among 15 analyzed individuals belonging to the same kindred. Our results link a defect in the amelogenin gene to the abnormal formation of enamel. We thus conclude that the amelogenin protein has a role in biomineralization of tooth enamel.  相似文献
4.
The "loss" of centromeres from chromosomes of aged women   总被引:6,自引:2,他引:4  
Both aneuploid cells in mitosis and nondisjunction in meiosis increase with advancing age. The cause(s) of these phenomena remains unknown. Here, it was confirmed that a positive Cd-band reflects the presence of a functioning centromere while a negative reaction is indicative of its inactivation or loss. We applied the Cd-banding technique to mitotic spreads obtained from 14 aged and 13 control females (peripheral blood culture). Of 6,474 scored chromosomes from the aged women, 62(0.96%) were Cd-negative; this was the case in 12 of 3,861 (0.31%) chromosomes from the younger controls. The difference was highly significant (P less than .001). About 60% of the 62 Cd-negative chromosomes from aged women belong to the C group. Chromosomes from six of the 14 aged females were additionally examined by either the C-band or the distamycin-DAPI technique; of 2,080 chromosomes, 13 (0.63%) showed premature separation of their centromeres (control: 7/5, 080, 0.14%). Our findings suggest that in aged women, the chromosomes tend to lose their Cd-positive material and the function of the centromere.  相似文献
5.
6.
7.
Distribution of break points in human structural rearrangements.   总被引:1,自引:0,他引:1       下载免费PDF全文
We attempted to resolve the issue on the location of breakages in patients with structural rearrangements, that is, whether they are located within the light band or are at the interface between a G-dark and a G-light band. Three types of structural rearrangements (inverted duplications, isodicentrics, and rings) were studied as they are capable of providing information not obtainable from other rearrangements because of reasons given in the RATIONALE. We found that break points are primarily located within the G-light bands; a small number of breaks are located in G-dark bands. Breakages at the interface were exceedingly rare. The possibility that they are, in fact, located at the interface of subbands within either light or dark bands appears tenuous. Contrary to what is described in the literature, terminal deletions are not useful in the determining of break points.  相似文献
8.
An average-sized human Y chromosome contains about 3,000 copies of the repeating DNA family DYZ1. A major repeating unit of the family, pHY10, has been cloned and an entire 3,564-bp sequence has already been determined by Nakahori et al. (1986). In the present study, pHY10 was divided into six consecutive segments, A to F, which were independently amplified by the PCR technique to see if they were strictly male-specific. pHY10 appears to consist of segments of various male-specificity. The B segment was apparently male-specific; however, the use of additional techniques (Southern-blot analysis or second PCR amplification in combination with the standard PCR) revealed homologous sequences in some females. None of the six segments of pHY10 may be male-specific in a strict sense. Different segments appear to be conserved during evolution to different extents. The 323-bp E segment appears to be the least conserved and to be responsible for the generation of most variations within the DYZ1 family.  相似文献
9.
DNA replication within the first 10 min of the S phase was studied using synchronized human diploid cells. It appeared that every chromosome in the human genome, including late-replicating X, had segment(s) which initiated DNA replication within the first 10 min of the S phase. The position, the shape and the size of these segments corresponded to those of Q(G)-negative bands suggesting that each of them constitutes a basic unit of initiation of DNA replication.  相似文献
10.
Fukuyama-type congenital muscular dystrophy (FCMD), the second most common form of muscular dystrophy in Japan, is an autosomal recessive severe muscular dystrophy associated with brain anomalies. After our initial mapping of the FCMD locus to chromosome 9q31-33, we have further defined the locus within a approximately 5-cM region between D9S127 and D9S2111 and have found linkage disequilibrium between FCMD and D9S306 in this candidate region on 9q31. The high prevalence of FCMD among the Japanese, who are a relatively isolated population, provides an opportunity to utilize linkage-disequilibrium mapping. We developed three new microsatellites, near D9S306, from the FCMD YAC contig, determined their positions on YACs, and performed linkage-disequilibrium mapping with these markers and other newly published loci. The maximum value of p(excess), which represents the strength of linkage disequilibrium, was obtained at D9S2107; and this value showed a relatively steady rise and fall across the region that is likely to contain FCMD. Distances between FCMD and each marker were presumed to be approximately 1 Mb, approximately 350 kb, approximately 140 kb, approximately 20 kb, approximately 280 kb, approximately 450 kb, and approximately 740 kb for D9S306, A107XF9, D9S2105, D9S2107, D9S172, D9S299, and D9S2109, respectively. Haplotype analysis using the three closest markers D9S2105, D9S2107, and D9S172 indicated that most FCMD-bearing chromosomes are derived from a single ancestral founder and suggested that these markers can be used for the diagnosis of sporadic FCMD. Thus, the FCMD gene is most likely to lie within a region of <100 kb containing D9S2107.  相似文献
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号