Abstract
A mutual translocation involving the Y and the second chromosomes was obtained by X-ray irradiation. The breakage of the second chromosome lies between the loci of the broken and brick and that of the Y chromosome is close to its distal end (Fig. 1). Both female and male individuals having the translocated chromosome IIp + Yd in extra are viable (Table 1 and 2). When such a fly carries the bobbed gene on the X chromosome, it shows an intermediate phenotype between the wild and bobbed (Fig. 6b). This is apparently due to the fact that the dominance of the wild allel of bobbed is reduced if the gene is contained in a translocated piece of the Y chromosome. Since the proximal halves of all the autosomes of D. virilis, except the sixth chromosome, are known to be made up of inert material, the extra chromosome seems to consist of a large part formed by the inert region of the second chromosome and a very small part formed by the Y chromosome. It is, therefore, concluded that the wild-type allel of bobbed is located close to the distal end of the Y chromosome.
