10° fichamento de genética em inglês

GENÉTICA DE PEIXES NEOTROPICAIS. II. BIOLOGIA
MOLECULAR DE PEIXES NEOTROPICAIS

ABSTRACT
Numerous studies were performed with molecular markers in 4
decades. This was possible due to the emergence of sophisticated techniques
resolution of proteins and DNA polymorphisms. With respect to
freshwater fish, whose Neotropics is characterized as the most
diverse in species number and population density, molecular biology
has provided several tools to access the genetic variation
existing in these groups and relate it to environmental factors and anthropogenic. This
so, there has been the emergence of articles dealing about genetic variation,
phylogenetic, phylogeographic, ecological, and other aspects of the biological dynamics
Fish. This paper aims to present a review
literature on the basic methodologies for the study of molecular biology,
front of the general trends of analysis in evolutionary biology of freshwater fish,
fresh from the Neotropics.
Keywords: fish, molecular markers, neotropics, biology
evolutionary

IntroductionAccording to Lewinsohn and Prado (2002), Brazilhouses the most diverse biota among the 17 mega-diverse countries on the planet. The fish are presented as thevertebrates more diverse and greater variationknown genetic. According to Lowe-McConnell(1999), there are approximately 20,000 species offish described and most currently inhabits waterswarm tropical oceans, with a total of40%. The freshwater fish are responsible for20 to 25% of vertebrate biodiversity and thereevidence that only occur in South Americamore than 8,000 species, with a view only twodescribed the various orders (Characiformes and Siluriformes). For Vari and Malabarba (1998), a percentage30 to 40% of all the diversity inNeotropical ichthyofauna was not yet recognized. Therefore it is primarily in the context ofidentification of diversity that are being appliedthe genetic and molecular markers in wildNeotropical fish, searching, including the exploitation of characteristics of economic interest andas evolutionarily significant units of conservation for the maintenance of biodiversity(Ryder, 1986).In the late 70's with the discoveryof restriction enzymes, began the first studies with molecular markers based on DNA.In subsequent years, the development of geneticpopulation gained momentum with the use of RFLP markers (restriction fragment lengthPolymorphisms). It was, however, with the emergenceof PCR (Polymerase Chain Reaction)that studies in this area have gained considerableexpression (Avise, 1994).Molecular biology has a wide areaof performance. Only for conservation genetics,has enabled estimates of heterozygosity, analysisfamily structures, occurrence of endemismbiodiversity value, identifying and monitoring the spread of invasive species (Solé-Cava,2001).This article aims to presenta literature review on the basic methodologiesstudy of molecular biology and correlatethem with the trends and needs of studies on the understanding, conservation, monitoring andrational exploitation of the diversity of biotafreshwater fishes in the Neotropics.Protein based markersThe explanation of the principle of variation for theisozyme polymorphism is simple: proteins areamino acid chains that reflect the expression ofan active gene in the DNA. The method consists basically on the principle of electrophoretic migration ofpolypeptide chains (isoenzymes), when subjectedto an electric field. The substitution of an amino acidthe chain can change its isoelectric point andits molecular mass, such that their migrationmay be different when exposed to electric current,thus reflecting the occurrence of variation in the sequence