Genomic organization of the Daphnia Trk relative to the vertebrate and amphioxus Trks. The diagram shows the part of the modular Trk protein encoded by each exon. The upper part of the diagram shows the different domains of the protein while the three diagrams below show the exon organization relative to these domains in vertebrates, amphioxus (Invertebrate deuterostome) and Daphnia (Protostome). SP: Signal Peptide; LRR: Leucine rich repeats; Cys rich: Cysteine rich domain; IG: Immunoglobulin domain; eJM: External Juxta-Membrane domain; TM: Transmembrane domain; Shc binding: Shc binding site; Tyrosine kinase: Tyrosine kinase domain; PLCg: Phospholipase C-γ docking site. Intron exon junctions are represented by vertical lines across the rectangle that represents each protein-coding sequence. Conserved intron-exon junctions between any invertebrate species and vertebrates are in red.