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Fig. 6 | BMC Evolutionary Biology

Fig. 6

From: Tracing the evolution of the heterotrimeric G protein α subunit in Metazoa

Fig. 6

Flexibility of exon-intron borders within the (pre)GNA12 and GNA13 genes. The positions of (pre)GNA12 and GNA13 exon borders (represented boxes) change across phylogeny. Box lengths correlate with average curated exon lengths (introns removed). a) preGNA12 (red) has three protein-coding exons in Placozoans, Cnidarians, Echinodermates, Hemichordates, and Cephalochordates. b) In Urochordates, the first exon of preGNA12 is divided into at least two exons while the final exon is divided into four exons. As the 5’ sequence is unresolved, more exons may be present (pink with ?). c) GNA12 exon-intron structure in jawed vertebrates (excluding euteleosts). The exon sequences upstream of exon3 are not resolved in either jawless vertebrate (lamprey) species investigated. The 5’ end of exon2 is extended by nine nt (pink) in all jawed vertebrates including euteleosts. d) GNA12 exon-intron structure in euteleosts (after 3R WGD but not in zebrafish) e) GNA13 (dark red) exon-intron structure in jawless vertebrates and cartilaginous fish. GNA13 arose after the 2R WGD that occurred before the emergence of vertebrates. Note that the exon border positions are identical to the GNA12 from (a). f) GNA13 exon-intron structure in lobe-finned fishes. The exon positions are identical to GNA12 in jawed vertebrates (except euteleosts) (c). The GNA13 sequence is extended by one split codon between exon1 and 2 and six nucleotides within exon2 (not shown). g) GNA13 exon border positons of euteleosts. The split codon and extended exon2 sequences are maintained

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