Randomly Amplified Polymorphic DNAs (RAPDs)

Abstract

Genetic variability or molecular biodiversity, besides being important for evolution, can be used as instrument of inquiry in diverse areas, for example, to verify the affinities and the limits between species, to detect forms of reproduction and familiar structure, to evaluate levels of migration and dispersion in populations and for the identification of species threatened with extinction. The basic data for these studies are the called molecular markers, which are genetic loci that present some variability, different rates of substitution/evolution between individuals, populations or species. In the past decade, several techniques have been developed for identifying and typing prokaryotic and eukaryotic organisms at the DNA level, which differ in their taxonomic range, discriminatory power, reproducibility, interpretation, and standardization. Molecular techniques using polymerase chain reaction (PCR)-based assays for DNA amplification have provided new insights into the systematic and evolutionary trends of different organisms. The most commonly used methods are PCR-hybridization, PCR-size polymorphism, random PCR-restriction fragment length polymorphism, and random amplified polymorphic DNA-PCR. However, one limitation for the immediate wide scale implantation of PCR technology, for genetic analysis of diverse organisms of interest, was the requirement of prior knowledge of the genome nucleotide sequences of the organisms for the design and synthesis of the primers. To solve this limitation, a PCRbased arbitrarily primed genetic assay called random amplified polymorphic DNA (RAPD), also referred to as arbitrarily primed PCR (AP-PCR) or DNA Amplification Fingerprinting (DAF), was described simultaneously by different authors (1-3) as a rapid and sensitive PCR method that enabled the identification of a large number of independent genetic loci representative of the target genome that are not biased towards particular sequences or types of sequences. The molecular markers of the RAPD type are now used world-wide for molecular studies, therefore they present Mendelian segregation (1) and can be used as genetic markers. © 2008 Humana Press.