Molecular characterization of ribosomal DNA polymorphisms discriminating among chromosomal forms of Anopheles gambiae s.s.

The sequence of a 2.3 kb long DNA segment derived from the 5'-most end of t he ribosomal intergenic spacer was determined in three chromosomal forms of Anopheles gambiae s.s. The analysis revealed that the sequence of the Mopt i form differed from that of the Bamako and Savanna forms by a total of ten nucleotide substitutions. Using these sequence variations we set up a diag nostic polymerase chain reaction (PCR) assay to distinguish mosquitoes belo nging to the three chromosomal forms, facilitating studies on the distribut ion and the ecology of these incipient taxa. The assay also allows to disti nguish whether a given specimen could represent a heterozygote between Mopt i and Savanna or Bamako.