共查询到20条相似文献，搜索用时 15 毫秒
1.
用等离子体浸没离子注入设备对食荚青豌种子进行了氩离子注入。以卢瑟福背散射（RBS）方法测定了处理前后的食荚青豌种子的RBS谱,发现等离子体浸没氩离子注入过的种子在Ar~+处出现Bragg峰。对食荚青豌根尖染色体核型进行了分析,发现所进行的离子注人能延迟染色体着丝粒的复制。 相似文献
2.
植物着丝粒的研究进展 总被引：1，自引：0，他引：1
着丝粒是许多高等真核生物染色体的重要结构域之一,它的最内层是由串联重复的卫星DNA及其侧翼富集的中度重复元件组成。在整个真核生物类群中,不同物种间着丝粒的DNA序列千差万别,但其功能却相当保守,可确保在有丝分裂和减数分裂过程中染色体的正确分离和传递。近年来,植物着丝粒的结构、功能和进化方面的研究进展较快,故对此进行了综述。 相似文献
3.
Genomic and genetic definition of a functional human centromere 总被引：1，自引：0，他引：1
Schueler MG Higgins AW Rudd MK Gustashaw K Willard HF 《Science (New York, N.Y.)》2001,294(5540):109-115
The definition of centromeres of human chromosomes requires a complete genomic understanding of these regions. Toward this end, we report integration of physical mapping, genetic, and functional approaches, together with sequencing of selected regions, to define the centromere of the human X chromosome and to explore the evolution of sequences responsible for chromosome segregation. The transitional region between expressed sequences on the short arm of the X and the chromosome-specific alpha satellite array DXZ1 spans about 450 kilobases and is satellite-rich. At the junction between this satellite region and canonical DXZ1 repeats, diverged repeat units provide direct evidence of unequal crossover as the homogenizing force of these arrays. Results from deletion analysis of mitotically stable chromosome rearrangements and from a human artificial chromosome assay demonstrate that DXZ1 DNA is sufficient for centromere function. Evolutionary studies indicate that, while alpha satellite DNA present throughout the pericentromeric region of the X chromosome appears to be a descendant of an ancestral primate centromere, the current functional centromere based on DXZ1 sequences is the product of the much more recent concerted evolution of this satellite DNA. 相似文献
4.
根据已报道的家猪着丝粒卫星DNA序列设计引物,对家猪基因组DNA进行PCR扩增,得到AC2卫星DNA序列。用PCR法将D ig-dUTP插入目的片段中得到标记DNA,然后利用荧光原位杂交方法检测13/17易位染色体。研究结果显示杂交信号位于所有端着丝粒染色体和13/17易位染色体的着丝粒区域,表明13号染色体和17号染色体虽然融合为一条亚中着丝粒染色体,但仍含有端着丝粒AC2卫星DNA,13/17易位染色体的AC2卫星DNA未发生缺失。 相似文献
5.
Salivary proline-rich protein genes on chromosome 8 of mouse 总被引：1，自引：0，他引：1
Endonuclease restriction (Hind III) fragments of DNA from Chinese hamster X mouse somatic cell hybrids hybridized with proline-rich protein complementary DNA clones only when the DNA was isolated from cells containing mouse chromosome 8, or a fragment of chromosome 8. The evidence suggests that proline-rich protein genes are located at the proximal portion of chromosome 8 toward the centromere. 相似文献
6.
植物着丝粒区串联重复序列的研究进展 总被引：1，自引：0，他引：1
着丝粒是细胞染色体的重要结构组成,控制姊妹染色单体的结合、动粒的组装和纺锤丝的附着,确保真核生物细胞在有丝分裂和减数分裂过程中染色体的正常分离及遗传信息的稳定传递。植物着丝粒DNA序列主要由反转录转座子和串联重复序列构成。串联重复序列在着丝粒功能实现和基因组进化过程中起重要作用。随着测序技术的成熟,近年来对串联重复序列的研究取得了很大的进展。综述了植物串联重复序列结构、分析方法及在进化中的作用,以期为相关研究提供参考。 相似文献
7.
目的:研究宿主蛋白KRT8对HBV复制的影响.方法:体外培养稳定表达HBV的肝癌细胞株(HepG2.2.15),分别用干扰KRT8基因的siRNA转染HepG2.2.15细胞和高表达KRT8基因的质粒转染HepG2.2.15细胞.RT-PCR验证转染效率,荧光定量PCR检测转染48小时后的细胞上清液HBV DNA水平.用拉米夫定抑制HepG2.2.15细胞HBV复制,RT-PCR检测基因表达水平.对数据采用t检验和方差分析,p<0.05为差异有统计学意义.结果:干扰KRT8基因表达后,HepG2.2.15细胞上清液中HBV DNA水平与对照组相比下降34%～38%(p<0.05).高表达KRT8基因后,HepG2.2.15细胞上清液中HBV DNA水平是对照组的28倍(p<0.01).抑制细胞HBV DNA复制后,HepG2.2.15细胞KRT8mRNA水平与对照组相比,下降了24%,但统计学无明显差异.结论:抑制宿主KRT8基因表达具有抗病毒作用. 相似文献
8.
An origin unwinding activity regulates initiation of DNA replication during mammalian cell cycle 总被引：26，自引：0，他引：26
An in vitro assay was developed to study the positive factors that regulate the onset of DNA replication during the mammalian cell cycle. Extracts prepared from cells at defined positions in the cell cycle were used to examine the replication of SV40 DNA in a cell free system. Extracts prepared from S phase cells were ten times more efficient at initiating replication at the SV40 origin than were extracts from G1 cells, whereas elongation rates were similar in G1 and S reactions. At a discrete point in the cell cycle, just before the cell's entry into S, an activity appeared that was required, in conjunction with SV40 T antigen, for site specific initiation at the SV40 origin. This factor had a role in unwinding DNA at the replication origin. 相似文献
9.
Copenhaver GP Nickel K Kuromori T Benito MI Kaul S Lin X Bevan M Murphy G Harris B Parnell LD McCombie WR Martienssen RA Marra M Preuss D 《Science (New York, N.Y.)》1999,286(5449):2468-2474
High-precision genetic mapping was used to define the regions that contain centromere functions on each natural chromosome in Arabidopsis thaliana. These regions exhibited dramatic recombinational repression and contained complex DNA surrounding large arrays of 180-base pair repeats. Unexpectedly, the DNA within the centromeres was not merely structural but also encoded several expressed genes. The regions flanking the centromeres were densely populated by repetitive elements yet experienced normal levels of recombination. The genetically defined centromeres were well conserved among Arabidopsis ecotypes but displayed limited sequence homology between different chromosomes, excluding repetitive DNA. This investigation provides a platform for dissecting the role of individual sequences in centromeres in higher eukaryotes. 相似文献
10.
A fluorescent staining technique has demonstrated a contralateral arrangement of fluorescent spots in the centromeric region of mouse metacentric chromosomes which have resulted from centric fusion. The results suggest that centric fusion involves the maintenance of DNA polaritv through the centromere and that the thymidine-rich chain of satellite DNA in the centromeric region is associated with the same DNA chain in every mouse autosome. 相似文献
11.
Cell cycle control of DNA replication by a homologue from human cells of the p34cdc2 protein kinase 总被引：52，自引：0，他引：52
The regulation of DNA replication during the eukaryotic cell cycle was studied in a system where cell free replication of simian virus 40 (SV40) DNA was used as a model for chromosome replication. A factor, RF-S, was partially purified from human S phase cells based on its ability to activate DNA replication in extracts from G1 cells. RF-S contained a human homologue of the Schizosaccharomyces pombe p34cdc2 kinase, and this kinase was necessary for RF-S activity. The limiting step in activation of the p34 kinase at the G1 to S transition may be its association with a cyclin since addition of cyclin A to a G1 extract was sufficient to start DNA replication. These observations suggest that the role of p34cdc2 in controlling the start of DNA synthesis has been conserved in evolution. 相似文献
12.
Pursell ZF Isoz I Lundström EB Johansson E Kunkel TA 《Science (New York, N.Y.)》2007,317(5834):127-130
Multiple DNA polymerases participate in replicating the leading and lagging strands of the eukaryotic nuclear genome. Although 50 years have passed since the first DNA polymerase was discovered, the identity of the major polymerase used for leading-strand replication is uncertain. We constructed a derivative of yeast DNA polymerase epsilon that retains high replication activity but has strongly reduced replication fidelity, particularly for thymine-deoxythymidine 5'-monophosphate (T-dTMP) but not adenine-deoxyadenosine 5'-monophosphate (A-dAMP) mismatches. Yeast strains with this DNA polymerase epsilon allele have elevated rates of T to A substitution mutations. The position and rate of these substitutions depend on the orientation of the mutational reporter and its location relative to origins of DNA replication and reveal a pattern indicating that DNA polymerase epsilon participates in leading-strand DNA replication. 相似文献
13.
Unwinding of duplex DNA from the SV40 origin of replication by T antigen 总被引：49，自引：0，他引：49
The T antigen specified by SV40 virus is the only viral-encoded protein required for replication of SV40 DNA. T antigen has two activities that appear to be essential for viral DNA replication: specific binding to duplex DNA at the origin of replication and helicase activity that unwinds the two DNA strands. As judged by electron microscopy, DNA unwinding is initiated at the origin of replication and proceeds bidirectionally. Either linear or circular DNA molecules containing the origin of replication are effective substrates; with closed circular DNA, a topoisomerase capable of removing positive superhelical turns is required for an efficient reaction. Presence of an origin sequence on duplex DNA and a single-strand DNA-binding protein appear to be the only requirements for T antigen to catalyze unwinding. This reaction mediated by T antigen defines a likely pathway to precise initiation of DNA replication: (i) the sequence-specific binding activity locates the origin sequence, (ii) the duplex DNA is unwound at this site, and (iii) the DNA polymerase and primase begin DNA replication. A similar pathway has been inferred for the localized initiation of DNA replication by bacteriophage lambda and by Escherichia coli in which a sequence-specific binding protein locates the origin and directs the DnaB helicase to this site. Observations with the SV40 system indicate that localized initiation of duplex DNA replication may be similar for prokaryotes and eukaryotes. 相似文献
14.
S phase of the cell cycle 总被引：21，自引：0，他引：21
In each cell cycle the complex structure of the chromosome must be replicated accurately. In the last few years there have been major advances in understanding eukaryotic chromosome replication. Patterns of replication origins have been mapped accurately in yeast chromosomes. Cellular replication proteins have been identified by fractionating cell extracts that replicate viral DNA templates in vitro. Cell-free systems that initiate eukaryotic DNA replication in vitro have demonstrated the importance of complex nuclear architecture in the control of DNA replication. Although the events of S phase were relatively neglected for many years, knowledge of DNA replication is now advancing rapidly in step with other phases of the cell cycle. 相似文献
15.
DNA分子标记检测种子纯度法的实验设计和统计评价 总被引：2，自引：0，他引：2
对ＤＮＡ分子标记检测蔬菜作物种子纯度法的实验设计和统计评价进行了分析。结果认为,分子标记检验蔬菜作物种子纯度时,进行两次重复较为合适,每次重复检测用种子数量相同,且以５０￣６０粒为宜。确定种子纯度时,可用点估计和区间估计;判定某一种子纯度是否属实时,应选用Ｕ检验法。 相似文献
16.
When DNA replication is inhibited during the synthesis (S) phase of the cell cycle, a signaling pathway (checkpoint) is activated that serves to prevent mitosis from initiating before completion of replication. This replication checkpoint acts by down-regulating the activity of the mitotic inducer cdc2-cyclin B. Here, we report the relation between chromatin structure and induction of the replication checkpoint. Chromatin was competent to initiate a checkpoint response only after the DNA was unwound and DNA polymerase alpha had been loaded. Checkpoint induction did not require new DNA synthesis on the unwound template strand but did require RNA primer synthesis by primase. These findings identify the RNA portion of the primer as an important component of the signal that activates the replication checkpoint. 相似文献
17.
Making sense of eukaryotic DNA replication origins 总被引：1，自引：0，他引：1
Gilbert DM 《Science (New York, N.Y.)》2001,294(5540):96-100
DNA replication is the process by which cells make one complete copy of their genetic information before cell division. In bacteria, readily identifiable DNA sequences constitute the start sites or origins of DNA replication. In eukaryotes, replication origins have been difficult to identify. In some systems, any DNA sequence can promote replication, but other systems require specific DNA sequences. Despite these disparities, the proteins that regulate replication are highly conserved from yeast to humans. The resolution may lie in a current model for once-per-cell-cycle regulation of eukaryotic replication that does not require defined origin sequences. This model implies that the specification of precise origins is a response to selective pressures that transcend those of once-per-cell-cycle replication, such as the coordination of replication with other chromosomal functions. Viewed in this context, the locations of origins may be an integral part of the functional organization of eukaryotic chromosomes. 相似文献
18.
Mitogen-induced replication of woodchuck hepatitis virus in cultured peripheral blood lymphocytes 总被引：9，自引：0，他引：9
Peripheral blood lymphocytes (PBLs) isolated from woodchucks chronically infected with the woodchuck hepatitis virus (WHV) carry low levels of nonreplicating WHV DNA. When PBLs from chronic carrier woodchucks were activated in culture with the generalized mitogen lipopolysaccharide (LPS), WHV DNA replication was initiated in cells obtained from one of three animals examined. Intracellular WHV core particles, containing WHV DNA replication intermediates, RNA/DNA hybrid molecules, and an active endogenous DNA polymerase, appeared 3 days after the start of LPS stimulation. After 5 to 7 days of LPS stimulation, WHV DNA-containing particles, which displayed the properties of intact, mature virions, were released into the culture medium. These studies provide evidence for reactivation of a latent WHV infection of circulating lymphoid cells and indicate that the presence of nonreplicating hepadnaviral DNA in lymphoid cells represents a potentially active infection following cellular activation. 相似文献
19.
东乡野生稻重复序列的克隆分析及染色体定位 总被引：3，自引：0，他引：3
从东乡野生稻(O ry za ruf ipogon G riff)中克隆到7个重复序列,序列分析表明:这些序列是与转座因子有关的序列。以序列H 2为探针,对不同基因组水稻进行Southern杂交,表明该序列为稻属内AA基因组特异的重复序列。其分布在水稻的多条染色体上,荧光原位杂交(F ISH)结果显示该重复序列主要位于染色体的着丝粒以及端粒附近,重复单位序列长度为615 bp左右。并就特异重复序列在水稻研究中的应用进行了讨论。 相似文献
20.
During meiosis in Saccharomyces cerevisiae, DNA replication occurs 1. 5 to 2 hours before recombination initiates by DNA double-strand break formation. We show that replication and recombination initiation are directly linked. Blocking meiotic replication prevented double-strand break formation in a replication-checkpoint-independent manner, and delaying replication of a chromosome segment specifically delayed break formation in that segment. Consequently, the time between replication and break formation was held constant in all regions. We suggest that double-strand break formation occurs as part of a process initiated by DNA replication, which thus determines when meiotic recombination initiates on a regional rather than a cell-wide basis. 相似文献