Rearrangements between germ-line Limited and somatic chromosomes in Smittia parthenogenetica (Chironomidae,Diptera)

Among more than 700 chromosome rearrangements induced by X-rays in oocytes of newly hatched females of Smittia parthenogenetica two cases of insertion of heterochromatin into an S chromosome have been obtained. As the S chromosomes do not contain such heterochromatic sections, the insertions must be derived from K chromosomes. Whether all K chromosomes are completely heterochromatic or whether all or some contain euchromatic sections remains open, but for the two latter possibilities no proof has been obtained. Euchromatic insertions or translocations with a banding pattern non-homologous with S chromosome sections have not been observed with certainty. Homologous duplications could all be interpreted as being derived from S chromosomes. From the K chromosome cycle it can be inferred that the K complement consists of more or less identical elements and that genetic isolation has led to their heterochromatinization.To Sally Hughes-Schrader with affection and admiration.