Fig. 2. Null mutations in skpA result in larval lethality. (A) Structure of the skpA gene, transcripts and mutations. The skpA transcript structures, site of the EP(X)1423 P-element insertion, and extent of the skpA deletion alleles are shown relative to the skpA genomic region. The skpA¹ deletion breakpoints were precisely mapped by sequencing; the extents of the other deletions are not known. P-element transformation of a 4 kb genomic fragment completely rescued the lethality associated with all four skpA alleles. (B) Survival of skpA^– larvae. Four-hour collections of embryos from the cross skpA¹/FM7, GFP x FM7, GFP/Y were aged from 1 to 5 days AED, and scored for the percentage of GFP^– larvae. Approximately 25% of larvae from a viable precise excision allele are GFP^– (skpA⁺/Y). Similarly, 25% of larvae from skpA mutant crosses are GFP^– immediately after hatching; however, this percentage steadily declines, indicating that skpA^–/Y larvae die at various points during larval development. (C) Growth of skpA^– larvae. The average cross-sectional area of GFP^– larvae from the previous cross are graphed (error bars equal one standard deviation). Wildtype and GFP⁺ sibling larvae increased in size 17-fold over 4 days, whereas skpA^– larvae only grew 6-fold.