Structure of Ribosomal Dna in Anopheles albimanus (Diptera: Culicidae)

Abstract

Anopheles albimanus Wiedemann has been described as the principal vector of malaria over much of its range in Central America, the Caribbean islands, and South America. Ribosomal DNA (rDNA) was cloned and characterized as a potential tool for studying the genetic variability of natural mosquito populations. The structure of the rDNA repeating unit was determined by restriction endonuclease mapping and hybridization analyses of genomic DNA from two laboratory colonies, four field populations, and 23 rDNA clones. The rDNA structure was similar to that observed in other Diptera in that it contained several hundred repeating units, each made up of a conserved ribosomal RNA coding region adjacent to a variable-length spacer region. By probing genomic DNA with spacer region subclones, we found that spacer regions varied in length within and among individual mosquitoes. Spacer length variability in individual mosquitoes was greater among different colonies and field populations than within colonies and populations. This finding suggests that rDNA spacer probes may be useful in analyzing the population structure of this medically important mosquito.