The lethal phenotype of the Df(3L)Z4-2.1, Df(3L)Z4-1.3 and Df(3L)Z4-7.1 chromosomes is rescued by the P{Z4myc} construct, which contains the complete Z4 gene, but not the complete CG12974 gene, suggesting that the lethality of the Df(3L)Z4-2.1, Df(3L)Z4-1.3 and Df(3L)Z4-7.1 chromosomes is due to an effect on the Z4 gene in each case.