MODIFICATION OF ABNORMAL GAMETIC RATIOS IN DROSOPHILA. I. EVIDENCE FOR AN INFLUENCE OF Y CHROMOSOMES AND MAJOR AUTOSOMES ON GAMETIC RATIOS FROM BAR-STONE TRANSLOCATION MALES

Abstract

IF one considers the meiotic behavior of two pairs of non-homologous chromosomes, designating one pair A and A’ and the other pair B and B’, then it is expected that A will separate from A’ and B from B’ and that, following a random assortment of the two pairs of chromosomes, four gametic types (AB, A’B’, AB’ and A’B) will be produced with, under ordinary circumstances, equal frequency. NOVITSKI and I. SANDLER (1957) reported a case in Drosophila melanogaster in which they showed that, despite the absence of evidence for departures from regular separation and random assortment in their experiments, certain gametic types were, nonetheless, recovered appreciably more frequently than others. They studied the kinds of gametes produced by Drosophila males carrying the Bar translocation of STONE, T ( 1 ;4) Bs, where A or XD represents the large distal piece of a broken X chromosome attached to the centric piece of a broken fourth chromosome, and A’ or IV a normal fourth chromosome, and where B or Xp represents the proximal centric piece of the broken X chromosome, marked with the mutant Bar, and having the remaining acentric piece of the broken fourth chromosome attached to its free end, and B’ or Y a normal Y chromosome (Figure 1 ) . The relative frequencies of the four gametic types, XD + Xp, IV -F Y, XD + Y, and IV 4- Xp, observed in their experiments are given below in row I, and the relative rates of recovery of the members of each homologous pair of chromosomes are given in row 111.