Gene Number in Selected Animal Genomes
| Species | Group | Gene number | Reference |
| Drosophila melanogaster | Arthropoda | 13,500 | Adams et al. 2000 |
| Caenorhabditis elegans | Nematode | 19,000 | The C. elegansSequencing Consortium 1998 |
| Ciona intestinalis | Urochordata | 15,500 | Simmen et al. 1998 |
| Fugu rubipiens | Actinopterygii | “similar to mammals” | Elgar 1996 |
| Homo sapiens | Mammalia | 80,000 | Antequera and Bird 1994 |
| 35,000 | Ewing and Green 2000; Roest Crollius et al. 2000; Lander et al. 2001; Venter et al. 2001 |