TABLE 1.

SPP mutants: lesions and tracheal phenotypes

Spp allele	Protein mutation	DNA mutation	Tracheal air filling (%)
Df(2L)lwr14	Fusion of aa 1–282 to 21 novel residues	1137-base deletion	15
Spp5	L → F 95	C → T 283	70
Spp6	K → stop 295	29-base deletion	0
Spp7	P → L 248	C → T 743	38

Four recessive lethal alleles of the Drosophila Spp gene are shown, along with a description of their genetic lesions and predicted effects on the resulting SPP proteins. The percentage of larvae with normal air filling is shown. A total of 95% of both wild-type and heterozygous Spp mutant animals had normal tracheal air filling.