RESUMO
The major sperm proteins (MSPs) are a family of closely related, small, basic proteins comprising 15% of the protein in Caenorhabditis elegans sperm. They are encoded by a multigene family of more than 50 genes, including many pseudogenes. MSP gene transcription occurs only in late primary spermatocytes. In order to study the genomic organization of transcribed MSP genes, probes specific for the 3' untranslated regions of sequenced cDNA clones were used to isolate transcribed genes from genomic libraries. These and other clones of MSP genes were located in overlapping cosmid clones by DNA fingerprinting. These cosmids were aligned with the genetic map by overlap with known genes or in-situ hybridization to chromosomes. Of 40 MSP genes identified, 37, including all those known to be transcribed, are organized into six clusters composed of 3 to 13 genes each. Within each cluster, MSP genes are not in tandem but are separated by at least several thousand bases of DNA. Pseudogenes are interspersed among functional genes. Genes with similar 3' untranslated sequences are in the same cluster. The six MSP clusters are confined to only three chromosomal loci; one on the left arm of chromosome II and two near the middle of chromosome IV. Additional sperm-specific genes are located in one cluster of MSP genes on chromosome IV. The multiplicity of MSP genes appears to be a mechanism for enhancing MSP synthesis in spermatocytes, and the loose clustering of genes could be a result of the mechanism of gene duplication or could play a role in regulation.
Assuntos
Caenorhabditis/genética , Genes , Proteínas Nucleares/genética , Pseudogenes , Animais , Sequência de Bases , Mapeamento Cromossômico , Cosmídeos , DNA/genética , Dados de Sequência Molecular , Hibridização de Ácido NucleicoRESUMO
Transcription terminators have been included in a phage-lambda-replicon-based cosmid vector, Lorist2, to insulate vector genes against transcriptional interference from cloned insert DNA. DNA yields of recombinant clones containing Escherichia coli genomic DNA inserts are more even for Lorist2 than with its progenitor LoristB. However, the terminators provide only a partial reduction in the over-representation of r X DNA-containing clones generally observed in cosmid libraries of Caenorhabditis elegans DNA, suggesting that causes other than transcriptional readthrough into the vector contribute to this problem.
Assuntos
Clonagem Molecular/métodos , Cosmídeos , Replicação do DNA , Genes Reguladores , Vetores Genéticos , Regiões Terminadoras Genéticas , Animais , Caenorhabditis/genética , Divisão Celular , Escherichia coli/genética , Regiões Promotoras GenéticasRESUMO
We have sequenced one complete rDNA tandem repeat from the nematode C. elegans. By comparative analysis we derive secondary structures for the 18s, 5.8s, and 26s rRNA molecules, and comment on other important features of the sequence. We also present the sequence of a junction between the rDNA and non-ribosomal DNA. Finally, we use our data to quantify the evolutionary relationships among several organisms currently studied in developmental biology.
Assuntos
Caenorhabditis/genética , DNA Ribossômico/genética , RNA Ribossômico , Sequência de Bases , Evolução Biológica , Clonagem Molecular , Genes , Conformação de Ácido Nucleico , RNA Ribossômico/genética , Homologia de Sequência do Ácido NucleicoAssuntos
DNA Mitocondrial , Aminoácidos/análise , Animais , Sequência de Bases , Bovinos , Códon , Replicação do DNA , Genes , Humanos , RNA Ribossômico , RNA de TransferênciaRESUMO
The complete sequence of the 16,569-base pair human mitochondrial genome is presented. The genes for the 12S and 16S rRNAs, 22 tRNAs, cytochrome c oxidase subunits I, II and III, ATPase subunit 6, cytochrome b and eight other predicted protein coding genes have been located. The sequence shows extreme economy in that the genes have none or only a few noncoding bases between them, and in many cases the termination codons are not coded in the DNA but are created post-transcriptionally by polyadenylation of the mRNAs.
Assuntos
DNA Mitocondrial/genética , Sequência de Bases , Evolução Biológica , Códon , Replicação do DNA , Genes , Humanos , Precursores de Ácido Nucleico/metabolismo , Iniciação Traducional da Cadeia Peptídica , Terminação Traducional da Cadeia Peptídica , RNA Ribossômico/genética , RNA de Transferência/genética , Transcrição GênicaRESUMO
Analysis of an almost complete mammalian mitochondrial DNA sequence has identified 23 possible tRNA genes and we speculate here that these are sufficient to translate all the codons of the mitochondrial genetic code. This number is much smaller than the minimum of 31 required by the wobble hypothesis. For each of the eight genetic code boxes with four codons for one amino acid we find a single specific tRNA gene with T in the first (wobble) position of the anticodon. We suggest that these tRNAs with U in the wobble position can recognize all four codons in these genetic code boxes either by a "two out of three" base interaction or by U.N wobble.
Assuntos
Anticódon/genética , Códon/genética , DNA Mitocondrial/genética , Código Genético , RNA Mensageiro/genética , RNA de Transferência/genética , Animais , Sequência de Bases , Evolução Biológica , Bovinos , Computadores , DNA Mitocondrial/análise , Humanos , Mamíferos/genética , Mitocôndrias , Uridina/análogos & derivadosRESUMO
A new method for determining nucleotide sequences in DNA is described. It is similar to the "plus and minus" method [Sanger, F. & Coulson, A. R. (1975) J. Mol. Biol. 94, 441-448] but makes use of the 2',3'-dideoxy and arabinonucleoside analogues of the normal deoxynucleoside triphosphates, which act as specific chain-terminating inhibitors of DNA polymerase. The technique has been applied to the DNA of bacteriophage varphiX174 and is more rapid and more accurate than either the plus or the minus method.
Assuntos
Sequência de Bases , DNA Viral , Colífagos/análise , DNA Polimerase I/antagonistas & inibidores , Enzimas de Restrição do DNA/metabolismo , Desoxirribonucleotídeos/farmacologia , MétodosRESUMO
A DNA sequence for the genome of bacteriophage phi X174 of approximately 5,375 nucleotides has been determined using the rapid and simple 'plus and minus' method. The sequence identifies many of the features responsible for the production of the proteins of the nine known genes of the organism, including initiation and termination sites for the proteins and RNAs. Two pairs of genes are coded by the same region of DNA using different reading frames.
