RESUMO
We sequenced a 173-kb region of mouse chromosome 10, telomeric to the Ifng locus, and compared it with the human homologous sequence located on chromosome 12q15 using various sequence analysis programs. This region has a low density of genes: one gene was detected in the mouse and the human sequences and a second gene was detected only in the human sequence. The mouse gene and its human orthologue, which are expressed in the immune system at a low level, produce a noncoding mRNA. Nonexpressed sequences show a higher degree of conservation than exons in this genomic region. At least three of these conserved sequences are also conserved in a third mammalian species (sheep or cow).
Assuntos
Cromossomos Humanos Par 12 , Interferon gama/genética , Telômero , Animais , Sequência de Bases , Cromossomos Artificiais Bacterianos , DNA Complementar , Expressão Gênica , Humanos , Camundongos , Dados de Sequência Molecular , Mapeamento Físico do CromossomoRESUMO
X chromosome inactivation in both mouse and human requires the presence of a cis acting locus, the X inactivation centre. This locus is thought to be involved in the initiation and spreading of the inactivation signal in early development. In order to increase our understanding of the mouse X inactivation centre, a 94 kb region immediately distal to the Xist gene has been sequenced and analysed for the presence of transcription units and/or potential cis acting regulatory elements. We have identified a novel gene, Tsx, lying 40 kb 3' from Xist. Tsx is expressed specifically in the testis and shows no convincing homology to proteins currently in the databases. A rat homologue, also X linked, has been isolated. The mouse and rat Tsx sequences are highly divergent, suggesting that part of the X inactivation centre, including both Xist and Tsx are subject to relatively weak evolutionary constraints.
Assuntos
Mecanismo Genético de Compensação de Dose , Proteínas/genética , RNA não Traduzido , Testículo/fisiologia , Fatores de Transcrição/genética , Animais , Composição de Bases , Sequência de Bases , DNA Complementar , Proteínas de Ligação a DNA , Regulação da Expressão Gênica no Desenvolvimento , Masculino , Camundongos , Dados de Sequência Molecular , Especificidade de Órgãos , RNA Longo não Codificante , RNA Mensageiro/análise , Proteínas de Ligação a RNA , Ratos , Mapeamento por Restrição , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Transcrição Gênica , Cromossomo XRESUMO
The statistical significance of amino acid sequence similarities previously observed in type II DNA methyltransferases has been investigated. It is shown: (1) that the intramolecular similarities observed among various type II Mtases are not statistically significant and thus can not be used to support a gene duplication model; (2) that the intermolecular similarities observed in a peptide in various type II adenine methylases are statistically confirmed; (3) that the similarities observed between MutH and these proteins for this peptide are not statistically significant and therefore cannot be used to propose a functional role in DNA recognition for this peptide.
Assuntos
Proteína O-Metiltransferase/genética , Homologia de Sequência de Aminoácidos , Sequência de Aminoácidos , Interpretação Estatística de Dados , Dados de Sequência Molecular , Família MultigênicaRESUMO
In an attempt to unify the genetic and biological research on Mycobacterium leprae, the aetiological agent of leprosy, a cosmid library was constructed and then ordered by a combination of fingerprinting and hybridization techniques. The genome of M. leprae is represented by four contigs of overlapping clones which, together, account for nearly 2.8Mb of DNA. Several arguments suggest that the gaps between the contigs are small in size and that virtually complete coverage of the chromosome has been obtained. All of the cloned M. leprae genes have been positioned on the contig maps together with the 29 copies of the dispersed repetitive element, RLEP. These have been classified into four groups on the basis of differences in their organization. Several key housekeeping genes were identified and mapped by hybridization with heterologous probes, and the current genome map of this uncultivable pathogen comprises 72 loci.
Assuntos
Cosmídeos , Biblioteca Gênica , Genoma Bacteriano , Mycobacterium leprae/genética , Mapeamento Cromossômico , Passeio de Cromossomo , Cromossomos Bacterianos , Impressões Digitais de DNA , DNA Bacteriano/genética , Hibridização In Situ , Sequências Repetitivas de Ácido NucleicoRESUMO
In Monte Carlo simulations of polymeric chains, the chains are most often represented as spheres, or cylinders with flat ends. In this methodological paper, we adopt a representation of the chains as spherocylinders (continuous cylinders ending in semispheres). With such a representation the testing for chain overlap, which is the crucial step for the inclusion of the excluded volume effect in the simulations, can be defined in a rigorous geometrical framework. The treatment we then derive fulfills the following features: it allows a very simple, automatic, and exhaustive classification of all the possible configurations; and it provides a physical representation for steric hindrance effects more natural than the flat-ended cylinders. Notably, this representation avoids the introduction of artificial anisotropies in the treatments. This spherocylindrical representation is also well suited for several types of calculations that can be involved in elaborate Monte Carlo simulations.
