共查询到20条相似文献，搜索用时 31 毫秒
1.
自1990年鱼腥藻PCC 7120中ntcA基因编码的蛋白被发现和鉴定以来,对其研究已取得一系列重要进展,其研究成果主要集中于ntcA基因及其编码蛋白的结构、功能及作用机制等方面,为更全面的了解鱼腥藻PCC 7120中的氮代谢和异形胞分化提供了线索。该研究分别从ntcA基因结构、其编码蛋白的功能、作用机制及作用范围等4个方面对鱼腥藻PCC 7120 ntcA基因的研究进展进行了简要综述。 相似文献
2.
蓝藻异型胞与生物固氮密切相关,同时也是蓝藻产氢的主要场所。采用17种无机盐,对两种蓝藻的异型胞分化进行诱导,实验结果表明：低渗水平浓度（0．05mol／L）的NaCl,MgCl2和MgSO4,既促进水华鱼腥藻（Anabaena flos—aquae）生长,又促进其异形胞的分化。其中,MgCl2对两者的促进作用最明显,分别比对照提高了1．5倍和1．2倍。17种无机盐中,只有MgSO4对念珠藻（Nostoc sp．）的生长和异形胞的分化都有促进作用,分别比对照提高了50％和56％。对两种藻的比较结果发现,无机盐对水华鱼腥藻的诱导作用明显大于念珠藻。 相似文献
3.
Transposition of cloned P elements into Drosophila germ line chromosomes 总被引：123，自引：0，他引：123
Recombinant DNA carrying the 3-kilobase transposable element was injected into Drosophila embryos of a strain that lacked such elements. Under optimum conditions, half of the surviving embryos showed evidence of P element-induced mutations in a fraction of their progeny. Direct analysis of the DNA of strains derived from such flies showed them to contain from one to five intact 3-kilobase P elements located at a wide variety of chromosomal sites. DNA sequences located outside the P element on the injected DNA were not transferred. Thus P elements can efficiently and selectively transpose from extrachromosomal DNA to the DNA of germ line chromosomes in Drosophila embryos. These observations provide the basis for efficient DNA-mediated gene transfer in Drosophila. 相似文献
4.
Amplification and enhanced expression of the epidermal growth factor receptor gene in A431 human carcinoma cells 总被引：46，自引：0，他引：46
G T Merlino Y H Xu S Ishii A J Clark K Semba K Toyoshima T Yamamoto I Pastan 《Science (New York, N.Y.)》1984,224(4647):417-419
The sequence of the human epidermal growth factor (EGF) receptor shows great homology with the avian erythroblastosis virus v-erb B oncogene, raising the possibility that the receptor gene is identical to the c-erb B protooncogene. Human A431 epidermoid carcinoma cells, which have an unusually high number of EGF receptors, were examined to determine whether elevated EGF receptor levels correlate with gene amplification. Southern blots of genomic DNA's from A431 and other human cell lines were probed with either a v-erb B gene fragment or a human EGF receptor complementary DNA clone (pE7), previously isolated from an A431 complementary DNA library. When either probe was used to analyze Eco RI- or Hind III-generated DNA fragments, EGF receptor DNA sequences were amplified about 30-fold in A431. Differences in the banding pattern of A431 DNA fragments relative to normal fibroblast DNA indicate the occurrence of a rearrangement in the region of the receptor gene. Furthermore, A431 cells contain a characteristic, prominent 2.9-kilobase RNA. These results are consistent with the hypothesis that, in A431 cells, gene amplification, possibly associated with a translocation event, may result in the overproduction of EGF receptor protein or the appearance of the transformed phenotype (or both). 相似文献
5.
6.
M A Goldman K R Stokes R L Idzerda G S McKnight R E Hammer R L Brinster S M Gartler 《Science (New York, N.Y.)》1987,236(4801):593-595
Mammalian X-chromosome inactivation involves a coordinate shutting down of physically linked genes. Several proposed models require the presence of specific sequences near genes to permit the spread of inactivation into these regions. If such models are correct, one might predict that heterologous genes transferred onto the X chromosome might lack the appropriate signal sequences and therefore escape inactivation. To determine whether a foreign gene inserted into the X chromosome is subject to inactivation, transgenic mice harboring 11 copies of the complete, 17-kilobase chicken transferrin gene on the X chromosome were used. Male mice hemizygous for this insert were bred with females bearing Searle's translocation, an X-chromosome rearrangement that is always active in heterozygous females (the unrearranged X chromosome is inactive). Female offspring bearing the Searle's translocation and the chicken transferrin gene had the same amount of chicken transferrin messenger RNA in liver as did transgenic male mice or transgenic female mice lacking the Searle's chromosome. This result shows that the inserted gene is not subject to X-chromosome inactivation and suggests that the inactivation process cannot spread over 187 kilobases of DNA in the absence of specific signal sequences required for inactivation. 相似文献
7.
Isolation of a novel receptor cDNA establishes the existence of two PDGF receptor genes 总被引：82，自引：0，他引：82
T Matsui M Heidaran T Miki N Popescu W La Rochelle M Kraus J Pierce S Aaronson 《Science (New York, N.Y.)》1989,243(4892):800-804
8.
Identification of DNA sequence responsible for 5-bromodeoxyuridine-induced gene amplification 总被引：1，自引：0，他引：1
Bromodeoxyuridine (BrdUrd) treatment of the prolactin nonproducing subclone of GH cells (rat pituitary tumor cells) induces amplification of a 20-kilobase DNA fragment including all of the prolactin gene coding sequences. This amplified DNA segment, which is flanked by two unamplified regions, thus designates a unit of BrdUrd-induced amplified sequence. Cloned DNA segments, 10.3 kilobases long, from the 5' end of the rat prolactin gene of BrdUrd-responsive and -nonresponsive cells, were ligated to the thymidine kinase gene of herpes simplex virus type 1 (HSV1TK), and the hybrid DNA was transferred to thymidine kinase-deficient mouse fibroblast cells by transfection. The HSV1TK gene and the rat prolactin gene were amplified together in drug-treated transfectants carrying the hybrid DNA HSV1TK gene and rat prolactin gene of BrdUrd-responsive GH cells. These results suggest that the 10.3-kilobase DNA segment at the 5' end of the rat prolactin gene of BrdUrd-responsive GH cells carries the information for drug-induced gene amplification (amplicon) and that another gene, such as the HSV1TK gene, is also amplified when the latter is placed adjacent to this segment. 相似文献
9.
10.
Clustering of human H1 and core histone genes 总被引：9，自引：0，他引：9
N Carozzi F Marashi M Plumb S Zimmerman A Zimmerman L S Coles J R Wells G Stein J Stein 《Science (New York, N.Y.)》1984,224(4653):1115-1117
An H1 histone gene was isolated from a 15-kilobase human DNA genomic sequence. The presence of H2A, H2B, H3, and H4 genes in this same 15-kilobase fragment indicates that mammalian core and H1 histone genes are clustered. 相似文献
11.
A large deletion within the T-cell receptor beta-chain gene complex in New Zealand white mice 总被引：16，自引：0，他引：16
The T-cell receptor beta-chain gene complex contains a duplication of D beta, J beta, and C beta gene segments in mice and man. When DNA from many inbred strains of mice was screened an unusual allele of the beta locus was identified in New Zealand White (NZW) mice. This allele is distinguished by the deletion of an 8.8-kilobase segment of DNA containing C beta 1, D beta 2 and the J beta 2 cluster. Despite the fact that all NZW T-cell receptors must be derived from a single set of beta-chain gene segments, this strain has functional T cells and is phenotypically normal. This deletion of T-cell receptor beta-chain segments occurs in a strain known to contribute to lupus-like autoimmune disease. 相似文献
12.
Interferon and c-ets-1 genes in the translocation (9;11)(p22;q23) in human acute monocytic leukemia 总被引：13，自引：0，他引：13
Gene probes for interferons alpha and beta 1 and v-ets were hybridized to metaphase chromosomes from three patients with acute monocytic leukemia who had a chromosomal translocation, t(9;11)(p22;q23). The break in the short arm of chromosome 9 split the interferon genes, and the interferon-beta 1 gene was translocated to chromosome 11. The c-ets-1 gene was translocated from chromosome 11 to the short arm of chromosome 9 adjacent to the interferon genes. No DNA rearrangement was observed when these probes were hybridized to genomic DNA from leukemic cells of two of the patients. The results suggest that the juxtaposition of the interferon and c-ets-1 genes may be involved in the pathogenesis of human monocytic leukemia. 相似文献
13.
Nucleotide sequence of a bovine clone encoding the angiogenic protein, basic fibroblast growth factor 总被引：117，自引：0，他引：117
J A Abraham A Mergia J L Whang A Tumolo J Friedman K A Hjerrild D Gospodarowicz J C Fiddes 《Science (New York, N.Y.)》1986,233(4763):545-548
Basic and acidic fibroblast growth factors (FGF's) are potent mitogens for capillary endothelial cells in vitro, stimulate angiogenesis in vivo, and may participate in tissue repair. An oligonucleotide probe for bovine basic FGF was designed from the nucleotide sequence of the amino-terminal exon of bovine acidic FGF, taking into account the 55 percent amino acid sequence homology between the two factors. With this oligonucleotide probe, a full length complementary DNA for basic FGF was isolated from bovine pituitary. Basic FGF in bovine hypothalamus was shown to be encoded by a single 5.0-kilobase messenger RNA; in a human hepatoma cell line, both 4.6- and 2.2-kilobase basic FGF messenger RNA's were present. Both growth factors seem to be synthesized with short amino-terminal extensions that are not found on the isolated forms for which the amino acid sequences have been determined. Neither basic nor acidic FGF has a classic signal peptide. 相似文献
14.
T M Williams D Moolten J Burlein J Romano R Bhaerman A Godillot M Mellon F J Rauscher J A Kant 《Science (New York, N.Y.)》1991,254(5039):1791-1794
15.
DNA methylation and gene function 总被引：235，自引：0，他引：235
In most higher organisms, DNA is modified after synthesis by the enzymatic conversion of many cytosine residues to 5-methylcytosine. For several years, control of gene activity by DNA methylation has been recognized as a logically attractive possibility, but experimental support has proved elusive. However, there is now reason to believe, from recent studies, that DNA methylation is a key element in the hierarchy of control mechanisms that govern vertebrate gene function and differentiation. 相似文献
16.
Chromosomal rearrangement generating a composite gene for a developmental transcription factor 总被引：73，自引：0，他引：73
Differential gene expression in the mother cell chamber of sporulating cells of Bacillus subtilis is determined in part by an RNA polymerase sigma factor called sigma K (or sigma 27). The sigma K factor was assigned as the product of the sporulation gene spoIVCB on the basis of the partial aminoterminal amino acid sequence of the purified protein. The spoIVCB gene is now shown to be a truncated gene capable of specifying only the amino terminal half of sigma K. The carboxyl terminal half is specified by another sporulation gene, spoIIIC, to which spoIVCB becomes joined inframe at an intermediate stage of sporulation by site-specific recombination within a 5-base pair repeated sequence. Juxtaposition of spoIVCB and spoIIIC need not be reversible in that the mother cell and its chromosome are discarded at the end of the developmental cycle. The rearrangement of chromosomal DNA could account for the presence of sigma K selectively in the mother cell and may be a precedent for the generation of cell type-specific regulatory proteins in other developmental systems where cells undergo terminal differentiation. 相似文献
17.
Unusual immunoglobulin gene rearrangement leads to replacement of recombinational signal sequences 总被引：12，自引：0，他引：12
An unexpected immunoglobulin gene rearrangement, signal sequence replacement, was observed in which the recombinational signal sequences of a VH gene segment are fused intact to the 5' end of a DJH element. Nucleotides are not lost from the signal sequences, but they may be lost from the DJH coding sequence. Signal sequence replacement may result from the alternative resolution of an intermediate in VH-to-DJH recombination. This type of rearrangement provides a means to alter the targeting of immunoglobulin gene segments and suggests a mechanism for the occurrence of VH-JH junctions in vivo. Signal sequence replacement may represent an additional pathway for the generation of antibody diversity. 相似文献
18.
J genes for heavy chain immunoglobulins of mouse 总被引：15，自引：0，他引：15
A 15,8-kilobase pair fragment of BALB/c mouse liver DNA, cloned in the Charon 4A lambda phage vector system, was shown to contain the mu heavy chain constant region (CHmu) gene for the mouse immunoglobulin M. In addition, this fragment of DNA contains at least two J genes, used to code for the carboxyl terminal portion of heavy chain variable regions. These genes are located in genomic DNA about eight kilobase pairs to the 5' side of the CHmu gene. The complete nucleotide sequence of a 1120-base pair stretch of DNA that includes the two J genes has been determined. 相似文献
19.
应用农杆菌介导法成功地将玉米转座子Ds导入粳稻(OryzasattvaI.subsp.japontca)中花11的花粉愈伤组织中,基因转化以对除草剂PPT有抗性的Bar基因和潮霉素抗性基因Hpt为选择标记.共获得了18个独立的转基因绿苗,其中单倍体11株,二倍体7株.转基因植株均抗除草剂BASTA.考查了二倍体植株种子后代(T1)对BASTA的抗性,7个株系的所有植株均抗BASTA,而未发生感抗分离,表明外源基因在转基因植株中是纯合的.PCR和Southernblotting的研究支持上述结果.对获得纯合转基因株系的各种方法做作了比较和讨论. 相似文献
20.