Weak segmentation phenotype. In most homozygous embryos there are short thickened buds rather than long Malpighian tubules and there are often more than four buds. The distribution of nuclei in the tubules in most cases is similar to the gut (no zigzag pattern), nests of nuclei are found in the region of origin of the tubules between the posterior midgut and hindgut. The ureter is almost completely deleted. Kr²⁹/Kr²⁸ transheterozygotes have a similar Malpighian tubule phenotype to Kr²⁸ homozygotes. Kr²⁹/Kr¹ transheterozygotes have a similar Malpighian tubule phenotype to Kr²⁹ homozygotes.

weak allele segments T2 and 3 and A1 deleted; A2-4 variably deleted.