A fine-structure gynandromorph fate map of the Drosophila head.

A gynandromorph fate map of the head of D. melanogaster was produced using 28 landmarks derived from one imaginal disc. An examination of the meaning of fine-structure mapping discloses that the sturt value observed between one pair of landmarks within a disc may approximate the relative physical distance of their progenitor cells at blastoderm, but for another pair of landmarks (assuming no directed cell movements), the sturt value may simply reflect their close geographic location at the time the cells are specified for their particular differentiation, a time much later in development when most cell division within the disc has come to an end. The formation of early developmental compartments has little effect on fate-map distances. Our analysis of the data suggests there are approximately ten cells present at the blastoderm stage that are head progenitors. Each blastoderm cell is likely to be the progenitor of a particular array of landmarks, but there is overlap between arrays from different blastoderm cells.