Mutant phenotype of transheterozygotes can be rescued when in combination with dx^ENU homozygotes.

Recessive lethal like alleles N^Ax-59b and N^Ax-59d. N^Ax-75c/+ is temperature-sensitive for pleiotropic effects; the variation in mutant expression with temperatures of 18^oC, 25^oC and 29^oC resembles that of N^Ax-59b and N^Ax-59d with some variation in detail (Portin, 1981). The Ax mutant phenotype increases with increasing dose of the allele (Portin, 1981).