Maternal-effect recessive lethal or semi-lethal. snl¹/snl¹ females crossed to normal males produce fewer that 10% of the expected number of sons. Lethality can be rescued by a paternally derived snl⁺ allele as demonstrated by the survival of exceptional sons but not daughters (i.e., snl⁺/0 but not snl¹/snl¹/Y) of the above mating. Lethality occurs during embryonic or early larval stages. snl¹/+ females crossed to snl¹/Y males produce normal offspring in a 1:1 sex ratio. Crosses between snl¹ males and females are nearly sterile, producing extreme sex ratios favoring females among surviving offspring. Data indicate that homozygosity for tra enhances and for dsx reduces the lethality of sons of snl¹ mothers. Complements both r and fu, nearby genes that also act as maternal-effect lethals.

Homozygous females produce less than 10% male offspring regardless of male genotype. Females are phenotypically indistinguishable fro wild type. Lethal action occurs during the embryonic and early larval stages.