Genetic evidence of an unorthodox chromosomal system in the lac insectKerria lacca(Kerr)

Abstract

SUMMARYThe colour difference (crimson and yellow) inKerria lacca(Kerr) was used to test the ‘Lecanoid’ system of chromosome behaviour proposed on cytological evidence. The colour strains bred true for colour. Reciprocal matings between the colour strains produced only crimson sons and daughters, confirming that the colour difference is not sex-linked and that the male is somatically a diploid. The phenotypes of the F2and the backcross generations differed according to the heterozygosity and the direction of cross of the F1parents, since heterozygous females produced two kinds of gamete but heterozygous males produced only the maternal kind. Thus, while elimination of the paternal gene and hence chromosome was confirmed during the formation of male sex-cells, demonstration of somatic diploidy of the male is not compatible with a ‘Lecanoid’ system inK. lacca. Instead, the available cytogenetic evidence is suggestive of a chromosome system with heterochromatization and elimination of the paternal chromosome-set confined to the male germ line.