Fig. 10.

Multiple transcripts are possible from the complex locus of GNAS. a Different mRNA transcripts can be produced from the GNAS locus through alternative splicing. The XXL-exon, though not examined herein, can be alternatively included into the transcript in exchange for exon1 or the XL-exon. In addition, Placentalia possess a cassette exon3 (light green) which can be included or excluded within the transcript; a non-canonical SS can also give rise to an extended exon4 (dark green) in the same species. Box lengths correlate with average curated exon lengths (intron lines do not). b Crystallographic tertiary structure of Mammalia Gαs (PDB ID 1AZT [55]) missing exon3. The C-terminus of exon2 (pink sphere) and N-terminus of exon4 (red sphere) are shown