Deletion in the internal sequences of the chimeric element (contains sequences originating from the 1A region of the X chromosome) that are present in the In(1)y2ps21cscws progenitor chromosome. This deletion does not include the 1A-RE insulator sequence.
Mutants show partial reversion of the sc mutant phenotype compared to the In(1)y2ps21cscws progenitor. Pigmentation of the abdomen is not altered relative to the In(1)y2ps21cscws progenitor.