Amino Acid Sequence|Animals|Caenorhabditis elegans|Cells, Cultured|Chickens|Cyprinodontiformes|Drosophila|Gene Expression Regulation|Genome|Mice|Molecular Sequence Data|Phylogeny|Protein Structure, Tertiary|Rats|Sequence Alignment|Sequence Analysis, Protein|Sequence Homology, Amino Acid|Species Specificity|Xenopus laevis|src Homology Domains|src-Family Kinases