RIBOSOMAL-RNA GENES IN MOSQUITOS - LOCALIZATION BY FLUORESCENCE IN-SITU HYBRIDIZATION (FISH)

Fluorescence in situ hybridization (FISH) was used to localize the 18S -28S ribosomal RNA gene clusters on the chromosomes of 15 mosquito spe cies belonging to the Anophelinae and Culicinae subfamilies. In the ge nus Anopheles the rRNA genes are localized on the heterochromatic arm of both sex chromosomes. The association between rRNA genes and sex de termining chromosomes also applies to the homomorphic karyotype of Cul icinae mosquitoes, at least in those cases in which localization of th e sex locus/loci has been determined. In these species ribosomal genes are often found within or adjacent to heterochromatic regions (C band s). Differences in the location of rRNA genes among and within genera suggest the occurrence of several chromosomal rearrangements during th e evolution of mosquitoes.