In females, nos protein accumulates in the germline stem cells (GSCs) located at the anterior tip of the germarium, which does not express bam. When the GSC divides, one cell remains at the tip and retains its GSC identity, whereas the other daughter moves away from the tip and initiates a differentiation program which includes significant accumulation of the bam protein and rapid down-regulation of the nos protein in region 2 of the germarium. As the cells cease to divide, the relationship between nos and bam expression inverts, culminating with high levels of nos, as bam expression is extinguished in the 16-cell cyst in region 3. By contrast, in males, nos is expressed both in the testicular GSCs and in their bam-expressing daughters.

bam and nos expression are reciprocal patterns in early germ cells.