Cytological, linkage and insecticide studies on a genetic sexing line in Anopheles stephensi Liston.

T(Y-D1)35 is a genetic sexing line in Anopheles stephensi (2n = 6; XX female, XY male) based on the translocation of the dieldrin resistance gene to the male determining chromosome. A cytological analysis demonstrated the presence of a 3 chromosome multiple translocation in which part of the Y chromosome formed the differential segment. An analysis of egg karyotypes enabled the segregation behaviour of the complex to be determined and only alternate and adjacent I segregations could be demonstrated. The breakpoint of the translocation in chromosome 3 was located using polytene salivary gland preparations. Linkage studies using chromosome three markers revealed contrasting effects of the translocation on recombination in this chromosome. An insecticide treatment method, based on the exposure of newly emerged adults, was developed enabling large numbers of individuals to be treated for the production of only males.