Search results for "Map"
showing 10 items of 3484 documents
Mapping of Friedreich's ataxia locus by identification of recombination events in patients homozygous by descent
1994
The Friedreich's ataxia locus (FRDA) maps on chromosome 9q13. Genetic data, obtained from a small number of recombination events, indicated that the FRDA locus might be located centromeric to the D9S15/D9S5 linkage group, the most probable order being cen-FRDA-D9S5-D9S111-D9S15-D9S110-qter. Recently, new centromeric markers have been reported. Analysis of these markers allowed us to localize the recombination breakpoint in some of the recombinant families. However, only one proximal recombination has been found with these markers. To increase the genetic information from FRDA families, we have analyzed the centromeric markers FR1, FR2, FR7, FR8, and FR5 in patients homozygous by descent. Th…
The human complement component C8B gene: structure and phylogenetic relationship
1993
The eighth component of human complement (C8) is a serum protein that consists of three chains (alpha, beta and gamma), encoded by three separate genes, viz., C8A, C8B, and C8G. In serum, the beta-subunit is non-covalently bound to the disulfide-linked alpha-gamma subunit. Using a full-length C8 beta cDNA probe, we isolated several clones from human genomic lambda DNA libraries. Four lambda clones covering the complete cDNA sequence were characterized by TaqI restriction mapping and were "shotgun" subcloned into M13. C8 beta-cDNA-positive clones were partially sequenced to characterize the 12 exons of the gene with sizes from 69 to 347 bp. All intron-exon junctions followed the GT-AG rule. …
Molecular diversity at the self-incompatibility locus is a salient feature in natural populations of wild tomato (Lycopersicon peruvianum)
1993
A cDNA encoding a stylar protein was cloned from flowers of self-incompatible wild tomato (Lycopersicon peruvianum). The corresponding gene was mapped to the S locus, which is responsible for self-incompatibility. The nucleotide sequence was determined for this allele, and compared to other S-related sequences in the Solanaceae. The S allele was used to probe DNA from 92 plants comprising 10 natural populations of Lycopersicon peruvianum. Hybridization was conducted under moderate and permissive stringencies in order to detect homologous sequences. Few alleles were detected, even under permissive conditions, underscoring the great sequence diversity at this locus. Those alleles that were de…
Divergent Evolution of an "Orphon" Historic Gene Cluster in Chironomus
1993
The histone genes of the midge Chironomus thummi thummi are organized in tandemly repeated gene groups, each containing the four core histone genes plus an H1 gene. These repetitive gene groups are found at five different loci, linked on one chromosomal arm. In addition to the clustered gene groups an isolated histone gene group exists which is found spatially separated on a different chromosome ("orphon" gene group). These orphon genes have been cloned and analysed in detail. Nucleotide sequence and in situ hybridization data suggest that the orphon gene group was established early during chironomid speciation, possibly by a transposition-like mechanism. This allowed the genes to be moved …
FISH mapping of 18S-28S and 5S ribosomal DNA, (GATA)n and (TTAGGG)n telomeric repeats in the periwinkle Melarhaphe neritoides (Prosobranchia, Gastrop…
2001
Spermatocyte chromosomes of Melarhaphe neritoides (Mollusca, Prosobranchia, Caenogastropoda) were studied using fluorescent in situ hybridization (FISH) with four repetitive DNA probes (18S rDNA, 5S rDNA, (TTAGGG)n and (GATA)n). Single-colour FISH consistently mapped one chromosome pair per spread using either 18S or 5S rDNA as probes. The telomeric sequence (TTAGGG)n hybridized with termini of all chromosomes whereas the (GATA)n probe did not label any areas. Simultaneous 18S-5S rDNA and 18S-(TTAGGG)n FISH demonstrated that repeated units of the three multicopy families are closely associated on the same chromosome pair.
Genetic, cytogenetic and developmental analysis of the Drosophila melanogaster tumor suppressor gene lethal(2)tumorous imaginal discs (l(2)tid)
1992
Abstract Three of the twenty recessive-lethal tumor suppressor genes of Drosophila cause imaginal disc tumors in the homozygously mutated state. One of these is the lethal(2)tumorous imaginal discs (l(2)tid) gene. Histo-logical preparations show the tumorous imaginal disc epithelium to consist of a mosaic of cells in monolayer and cells in clumped arrangement. In contrast, the wild-type imaginal disc epithelium is comprised exclusively of cells in monolayer arrangement. Mutant imaginal disc tissue pieces implanted into ready-to-pupariate wild-type larvae fail to differentiate. Implantation of l(2)tid imaginal disc tissue pieces in vivo into wild-type adult flies revealed a lethal, tumorous …
Genetic and molecular analysis of six tumor suppressor genes in Drosophila melanogaster
1990
Six Drosophila melanogaster tumor suppressor genes causing malignant or benign tumors in specific cell types are described. The wild-type alleles of these genes are instrumental in the differentiation of particular cell types. In the homozygous state, recessive mutations in the genes interrupt the differentiation of the cells and thus cause their uncontrolled, autonomous, lethal proliferation. The tumors show all major characteristics of malignant and benign neoplastic growth. Genomic sequences of four of the genes have been identified and are currently being characterized. ImagesFIGURE 1.FIGURE 2.FIGURE 2.
rRNA gene restriction patterns and biotypes of Shigella sonnei.
1993
SUMMARYShigella sonneiis a major agent of diarrhoeal disease in developed as well as in developing countries. Several phenotypic methods to define strain differences have been applied to this species ofShigellaincluding, more recently, analysis of extrachromosomal and chromosomal DNA.In this study, 432 endemic and epidemic strains isolated between 1975 and 1991 in Italy, France and Switzerland were submitted to rRNA gene restriction pattern analysis, after digestion of whole-cell DNA byHincII, and to concomitant biotyping.Thirteen ribotypes, HI to H13, and five biotypes, a, d, e, f, g, were detected. Xinety-five percent of the sporadic strains were assigned to ribotypes HI to H4, which coul…
Further characterization of the histidine gene cluster of Streptomyces coelicolor A3(2): nucleotide sequence and transcriptional analysis of hisD.
1992
We have further characterized the genomic region of Streptomyces coelicolor A3(2) that contains genes involved in the biosynthesis of histidine. A 2,357-base pair fragment contained in plasmid pSCH3328 that complemented hisD mutations has been sequenced. Computer analysis revealed an open reading frame that encodes a protein with significant homology to the Escherichia coli, Salmonella typhimurium and Mycobacterium smegmatis hisD product, Saccharomyces cerevisiae HIS4C, and Neurospora crassa his3 gene products. Two other contiguous open reading frames oriented divergently with respect to hisD did not show significant similarity with any of the his genes or to other sequences included in the…
The evolution of dosage-compensation mechanisms
2000
Dosage compensation is the process by which the expression levels of sex-linked genes are altered in one sex to offset a difference in sex-chromosome number between females and males of a heterogametic species. Degeneration of a sex-limited chromosome to produce heterogamety is a common, perhaps unavoidable, feature of sex-chromosome evolution. Selective pressure to equalize sex-linked gene expression in the two sexes accompanies degeneration, thereby driving the evolution of dosage-compensation mechanisms. Studies of model species indicate that what appear to be very different mechanisms have evolved in different lineages: the male X chromosome is hypertranscribed in drosophilid flies, bot…