a) Top panel shows the results for PCR using templates derived from human lens and mouse whole eye cDNA libraries. Positions of PCR primers relative to mouse gene exon structure are shown schematically. Mouse clones quantitatively include exon 3 which is efficiently skipped in human clones
b) Sequence alignment of exon 3 ORF amino acid sequences from mammalian lengsin genes. Predicted sequences of chimp and rhesus monkey exon 3 ORF are included for comparison, although the splice sites in these species have not yet been experimentally verified.