Figure 2.—

Guanine-to-adenine transition in levy¹ DNA resulted in missplicing of CG17280 RNA. (A) levy¹ DNA contained an adenine nucleotide at the 3′-splice junction within the intron of CG17280 gene. This position was occupied by guanine in the wild-type gene as given in the BDGP database as well as in our own sequence determination of the region in CS and a sibling strain to levy¹. The 5′- and 3′-intron splicing consensus sequences are underlined. The G-to-A transition caused the levy¹ RNA to be misspliced by 1 nucleotide and resulted in a reading frame shift in exon 2, as determined by RT–PCR analysis of mutant levy RNA. (B) A schematic of missplicing of levy¹ RNA. Translated regions are shown as rectangles with the wild type shown as open rectangles. The shift in reading frame would presumably lead to replacement of 77 amino acids encoded by exon 2 with 22 missense amino acids (shaded rectangle). (C) Sequencing of levy¹ cDNA confirmed the occurrence of missplicing in levy¹ RNA. A portion of the levy¹ cDNA sequence is shown with the deduced amino acid (AA) sequence. The wild-type cDNA sequence and deduced amino acid translation are shown for comparison to those of the levy¹ mutant. The aberrant amino acid sequence resulting from a shift in the reading frame is shown in italics.