Assuntos
Conservação dos Recursos Naturais , Peixes/genética , Repetições de Microssatélites/genética , Animais , Oceano Atlântico , Sequência de Bases , DNA/química , Primers do DNA/química , Eletroforese em Gel de Ágar/veterinária , Biblioteca Gênica , Dados de Sequência Molecular , Reação em Cadeia da Polimerase/veterinária , Análise de Sequência de DNA/veterináriaRESUMO
Considerable controversy has surrounded the application of mitochondrial DNA data to reconstruction of evolutionary relationships among the endemic cichlids of Lake Malawi. Central to this debate has been the issue of whether lineage sorting is complete, and thus whether these data actually reflect species phylogeny, or simply gene genealogy. Review of all mtDNA control region sequences available for members of one monophyletic subset of this species flock, the Malawi rockfishes, or mbuna, strongly indicates that lineage sorting is incomplete: Character-based analyses of these sequences reconstruct gene, not species, interrelationships. Analysis of the pattern of nucleotide substitutions differentiating these mtDNA alleles suggests that pyrimidine residues undergo transition substitutions more often than do purines. Estimation of the magnitude of derived sequence differentiation in light of the reconstructed gene genealogy suggests that the mbuna may be of considerably more recent vintage than previous molecular characterizations have indicated.
Assuntos
DNA Mitocondrial/genética , Peixes/genética , África , Animais , Sequência de Bases , Evolução Biológica , Dados de Sequência Molecular , Filogenia , Homologia de Sequência do Ácido Nucleico , Especificidade da EspécieRESUMO
Atlantic haddock of Georges Bank are characterized by large fluctuations in population size and a recent collapse of the commercial fishery. DNA extracted from dried scales of Georges Bank haddock, archived by the U.S. National Marine Fisheries Service (NMFS), reveals significant heterogeneity in frequencies of four mitochondrial DNA control region haplotypes between 1975 and 1985 cohorts. Several processes may be responsible for this temporal variation, the most attractive hypothesis being that haddock from other geographic regions episodically contribute to the Georges Bank gene pool. Thus, the population of haddock spawning on Georges Bank may not be genetically discrete and, with respect to Atlantic haddock, Georges Bank may not be viewed as a closed system.
Assuntos
DNA Mitocondrial/genética , Peixes/genética , Variação Genética/genética , Animais , Oceano Atlântico , Sequência de Bases , Haplótipos , Dados de Sequência Molecular , Polimorfismo de Fragmento de Restrição , Análise de Sequência de DNARESUMO
Three variable microsatellite loci have been isolated from the American lobster, Homarus americanus. In a population sample from the Gulf of Maine, the effective numbers of alleles (Ne) for the two most variable loci were 16.33 and 13.19, respectively. Reduced variability at all three loci was seen in the European lobster, H. gammarus, for which the maximum Ne was 4.00. The reduction in variability in H. gammarus is consistent with a bottleneck event. Inheritance analysis using H. americanus demonstrated segregation of codominant alleles and the absence of linkage. Null alleles were observed at two loci in inheritance studies. This study demonstrates that microsatellite loci should be useful in studying the population structure of clawed lobsters.
Assuntos
DNA/genética , Repetições de Microssatélites/genética , Nephropidae/genética , Animais , Feminino , Frequência do Gene , Variação Genética/genética , Maine , Polimorfismo GenéticoRESUMO
Numerous molecular systematic studies have employed variation in the mitochondrial large subunit (16s) rRNA gene to infer patterns of relationship among species and higher taxa. The primers most commonly employed in 16s rRNA amplification and sequencing bracket an approximately 600 bp portion of this gene. However, most of the informative variation occurs within a 200 bp subset of this segment. We describe a novel primer pair designed to amplify this variable region in a wide range of taxa, allowing broader application and considerable streamlining of data acquisition for studies using this gene.
Assuntos
Primers do DNA/química , Mitocôndrias/genética , Filogenia , Reação em Cadeia da Polimerase/métodos , RNA Ribossômico 16S/genética , Animais , Sequência de Bases , Aves/genética , Sequência Conservada , DNA Mitocondrial/genética , Drosophila melanogaster/genética , Peixes/genética , Variação Genética , Modelos Genéticos , Dados de Sequência Molecular , Nephropidae/genética , Homologia de Sequência do Ácido NucleicoRESUMO
The SATA satellite DNA family of sequences, composed of three size variants of approximately 237, 230, and 209 bp, is conserved in the genomes of tilapiine and haplochromine cichlid fishes. In the present study we examined the utility of the SATA sequences for inferring phylogenetic relationships among the three major genera of tilapiine fishes, Oreochromis, Sarotherodon, and Tilapia. Hybridization of the monomer SATA repeat to genomic DNA of representative cichlid species established conservation of the sequence in the African tilapine and haplochromine lineages and its absence from other cichlid lineages. Bootstrapped DNA parsimony and neighbor-joining analyses of derived consensus sequences revealed two distinct clades, one containing the mouthbrooding genera Oreochromis and Sarotherodon, and the other containing the substrate spawning genus Tilapia. These results are consistent with recent independent studies using mitochondrial DNA and establish the utility of the SATA satellite DNA family for phylogenetic reconstruction. Concerted evolution of the SATA sequences was also demonstrated within the tilapiine tribe.
Assuntos
DNA Satélite/genética , Filogenia , Tilápia/classificação , Animais , Sequência de Bases , Clonagem Molecular , DNA , Dados de Sequência Molecular , Homologia de Sequência do Ácido Nucleico , Tilápia/genéticaRESUMO
Progeny from single pair crosses of Atlantic herring were examined to determine the heritability of genetic variation at seven polymorphic allozyme loci. Mendelian inheritance of codominant autosomal alleles was established for IDH-2, LDH-1, LDH-2, ME-2, PGM-1, and PGI-2. This demonstration of Mendelian inheritance is essential for accurate interpretation of allozymic variation among natural populations of this pelagic species.