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Results for “repeated DNA sequences”

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At least 235 records · Page 13Linked to original sources
PubMed1992

Repeated DNA sequences of Aegilops markgrafii (Greuter) Hammer var. markgrafii: cloning, sequencing and analysis of distribution in Poaceae species.

Total DNA of Aegilops markgrafii (Greuter) Hammer var. markgrafii was shot gun cloned. From all the recombinants containing repetitive sequences 1-2% hybridized preferentially with the Ae. markgrafii genome and were almost absent in wheat. The cloned sequences are disperse distributed over the Aegilops chromosomes and show the typical features of eukaryotic repetitive DNA. Five specific probes were tested for their applicability in a screening program on 68 Poaceae accessions.

Base Sequence↗
PubMed1980

Recombination of dispersed repeated DNA sequences in yeast.

Yeast transformation can be used to insert new sequence arrangements into a variety of chromosomal locations by homologous recombination. These newly inserted sequences can recombine with similar sequences located on other chromosomes. In these events, information is duplicated without being lost at the site from which it is derived. Similar mechanisms might be utilized by cells to provide new functions during development or differentiation.

Base Sequence↗
PubMed1991

Repeated DNA sequence involved in mutations affecting transport of sucrose into Streptococcus mutans V403 via the phosphoenolpyruvate phosphotransferase system.

Mutants of Streptococcus mutans V403 defective in the intracellular sucrose-6-phosphate hydrolase (product of the scrB gene) are sensitive to sucrose because of the intracellular accumulation of the phosphorylated sugar. Using a scrB mutant prepared by allelic exchange, we have isolated and characterized a number of sucrose-resistant revertants. One such mutant was found to lack the ability to transport sucrose into the cell via the phosphoenolpyruvate-dependent sucrose phosphotransferase system (PTS). Genetic analysis of this strain revealed this lesion to be linked to the scrB gene. This was corroborated by the physical demonstration of an insertion mutation very near scrB. Taken together with DNA sequence information (Y. Sato, F. Poy, G. R. Jacobson, and H. K. Kuramitsu, J. Bacteriol. 171:263-271, 1989), our results indicated that all of the mutations characterized were located in the adjoining scrA gene which encodes the membrane-associated, sugar-specific enzyme II (EIIsucrose) component of the sucrose PTS in S. mutans. Biochemically, such a genetic lesion disables the sucrose PTS and prevents sucrose from entering the cell by this system. In this paper, we detail the nature of two independent insertion mutations and conclude them to be the result of duplicative transposition events into the scrA gene. This region of the chromosome was amplified and purified in large quantities by using the polymerase chain reaction. Examination of the amplified DNA revealed that the two independent insertion mutations were composed of sequences that were indistinguishable by size and by restriction site endonuclease maps. Their insertion points in the scrA gene were approximately 200 bp apart. The amplified DNA fragment was also used as a probe to demonstrate the presence of five copies of this element on the S. mutans V403 chromosome. A second strain, S. mutans V310, also was found to carry similarly arranged, multiple copies of this sequence on its chromosome, suggesting a clonal origin of V403 and V310. The small size of this sequence, its presence in multiple copies on the V403 chromosome, and its ability to duplicate itself semiconservatively into remote sites argue compellingly that it is an insertion sequence element. One such insertion mutant, with a defective sucrose PTS, was tested for virulence in rats and was found to cause caries at levels similar to those of the wild-type strain.

Animals↗
PubMed2003

Distribution of highly repeated DNA sequences in species of the genus Lens Miller.

Multiple-target fluorescence in situ hybridization (FISH) was applied on mitotic chromosomes of seven Lens taxa using two highly repetitive sequences (pLc30 and pLc7) isolated from the cultivated lentil and the multigene families for the 18S-5.8S-25S (pTa71) and 5S rRNA (pTa794) from wheat simultaneously as probes. The number and location of pLc30 and pLc7 sites on chromosomes varied markedly among the species, whereas the hybridization pattern of 5S rDNA and 18S-5.8S-25S rDNA was less variable. In general, each species showed a typical FISH karyotype and few differences were observed among accessions belonging to the same species, except for the accessions of Lens odemensis. The most similar FISH karyotype to the cultivated lentil is that of Lens culinaris subsp. orientalis, whereas Lens nigricans and Lens tomentosus are the two species that showed the most divergent FISH patterns compared with all taxa for number and location of pLc30 and 18S-5.8S-25S rDNA sites.

Chromosomes, Plant↗
PubMed1981

A cloned repeated DNA sequence in human chromosome heteromorphisms.

A sequence derived by ECoRI restriction of human satellite DNA III has been cloned in lambda gt WES. The cloned DNA was used as a template for in vitro synthesis of cRNA, which was hybridized in situ to preparations of human metaphase chromosomes with a range of heterochromatic polymorphisms. Most of the hybridization was found on chromosome 1, and the amount of hybridization was related to the size of the C-band on this chromosome. Hybridization to other chromosomes was not related to the C-band size, although hybridization of total satellite DNA is proportional to C-band size. Total satellite DNAs contain a mixture of sequences, some of which are predominantly located on only one pair of chromosomes. Hybridization in situ is able to discriminate between such chromosome-specific sequences and the bulk of satellite DNA. Further analysis of satellite DNAs may identify sequences specific for every chromosome pair.

Base Sequence↗
PubMed1975

Hybridization of mouse leukemia virus c-DNA to mouse repeated DNA sequences.

Experiments of hybridization between mouse leukemia virus synthetic 3H-DNA probe and mouse main band and satellite DNAs indicate that there is not a higher concentration of viral sequences in the satellite DNA. On the contrary, viral sequences appear to be enriched in the fast renaturing intermediate main band DNA.

Animals↗
PubMed2002

Polymorphisms in the cell wall-spanning domain of the C protein beta-antigen in clinical Streptococcus agalactiae isolates are caused by genetic instability of repeating DNA sequences.

The C protein alpha- and beta-antigens are immunodominant components of the surface of Streptococcus agalactiae, the most frequent cause of neonatal sepsis. Both proteins are thought to contribute significantly to virulence of S. agalactiae. They are mainly expressed by serotypes Ia, Ib, and II. The C protein beta-antigen (Cbeta-protein) binds to the Fc portion of human IgA and seems to be of importance in bacterial resistance to mucosal immune defense mechanisms. In this study, PCR analysis of S. agalactiae isolates obtained from 189 neonates and 112 pregnant women revealed the presence of the Cbeta-protein gene in 19% and 22% of the isolates, respectively. Size polymorphisms of the PCR products within the gene region encoding the cell wall-spanning domain indicated a high degree of genetic variability. Thirteen different variants of the amplified region were differentiated among the 60 Cbeta-protein-positive isolates by sequence analysis. In all variants, the polymorphisms were caused by insertions and deletions of repetitive DNA elements that did not alter the open reading frame. Comparison of the Cbeta-protein gene polymorphisms showed a significantly higher rate of isolates carrying deletions >50 bp in serotype Ib than in serotype II isolates (p = 0.001); this was also true for neonatal isolates analyzed separately (p = 0.01). Neonatal isolates carried a higher rate of large deletions when compared with maternal isolates; this difference, however, did not reach statistical significance (p = 0.08). We hypothesize that polymorphisms in the cell wall-spanning domain of the Cbeta-protein are of functional relevance with regard to maternofetal transmission of the pathogen.

Adult↗