Figure 3.

Cytogenetic map of the Y chromosome of D. melanogaster. At the top is a photomicrograph of the banding pattern of a Hoechst-stained Y chromosome. Below are diagrammatic representations of the banding revealed by differential staining of the Y. The darker blocks correspond to more brightly-staining regions. The position of the centromere is indicated by a constriction and the letter c. Genetic mapping has positioned the YL (kl-5, kl-3, kl-2, and kl-1) and YS (ks-1 and ks-2) male fertility factors in the dim regions adjacent to the bright blocks. The bobbed locus or nucleolus organizer region (ribosomal RNA cistrons) is in YS between the bright blocks at the centromere and the distal pair at the telomere of the short arm.