Reduced viability, especially of females; abnormalities of posterior legs, also especially in females. fs(1)K451/Df(1)g-l does not survive. Homozygous females produce eggs with short thin dorsal appendages and ultrastructurally defective chorions. All major chorion proteins underproduced owing to failure of chorion protein gene amplification. Cp genes on the third chromosome more severely affected than those on the X (Orr, Komitopoulou, and Kafatos, 1984, Proc. Nat. Acad. Sci. USA 81: 3773-77). In mosaic experiments fs(1)K451 behaves as a locus required in both somatic and germinal tissues (Perrimon and Gans, 1983, Dev. Biol. 100: 365-73).

Survival of homozygous and hemizygous larvae hypersensitive to exposure to methyl methanesulfonate, nitrogen mustard, 2-acetylaminofluorene, and gamma rays. Partially deficient in post-replication repair (Boyd and Setlow, 1976; Brown, and Boyd, 1981, Mol. Gen. Genet. 183: 356-62); nitrogen-mustard mutagenesis abolished; mus101+ implicated in recovery from DNA crosslinking (Graf, Green, and Wurgler, 1979, Mutat. Res. 63: 101-12). Displays hypermutability to alkylating agents; defective in alkylation repair pathway (Smith and Dusenberg, 1988, Mechanisms and Consequences of DNA Damage Processing, Alan R. Liss, Inc., pp. 251-55). Increases X-ray-induced post-meiotic chromosome loss (Cooper and Zimmering, 1981, Mutat. Res. 81: 345-56). Mutants inhibit premeiotic rDNA magnification in males (Hawley, Marcus, Cameron, Schwartz, and Zitron, 1985, Proc. Nat. Acad. Sci. USA 82: 8095-99). mus101 function required for chorion-gene amplification (Snyder, Galanopoulous, and Kafatos, 1986, Proc. Nat. Acad. Sci. USA 83: 3341-45). Homozygotes for female-fertile allele exhibit elevated meiotic nondisjunction (Boyd et al., 1976). Causes mitotic chromosome instability (mus101D1, Baker and Smith, 1979, Genetics 92: 833-47), and defective mitotic condensation of heterochromatin (musts1, Gatti, Smith, and Baker, 1983, Science 221: 83-85).