Studies of the X chromosome of Anopheles albimanus
Snow (sn) is a recessive, eye color mutant that is phenotypically indistinguishable from the previously described mutant, white eye (we). The loci for these mutants are over 30 map units apart on the X chromosome. Analysis of salivary gland chromosomes of radiation-induced X-autosome translocations were used to define the positions of sn and we on the distal euchromatic portion of the long arm of the X chromosome. A recessive lethal trait (bubble head) was also mapped relative to we and sn, and the gene order on the long arm of the X chromosome is as follows: centromere – ? – snow – bubble head – white eye. Translocation breakpoints in the euchromatic portion of the X chromosome caused sterility or lethality in males hemizygous for the translocations, but breaks in the heterochromatin had no effect. Crossing-over was greatly reduced when translocation breakpoints were located in the euchromatic part of the X chromosome. The translocations were used to determine that the nucleolar organizer region is probably on the short arm of the X chromosome.Key words: Anopheles albimanus, eye colour mutant, X chromosome.