Glossary of "Plant Systematics (1st ed.)" by Simpson (2006)
- One of two or more different molecular forms of an enzyme, corresponding to different alleles of a common gene.
Glossary of "Evolution (4th ed.)" by Futuyma & Kirkpatrick (2017)
- One of several forms of an enzyme encoded by different alleles at a locus, that are distinguished by gel electrophoresis.
Glossary of "Genetic Management of Fragmented Animal and Plant Populations" by Frankham et al. (2017)
- Alternative forms of a protein detected by electrophoresis and protein staining that are due to alternative alleles at a single locus.
Glossary of "Molecular Systematics (2nd ed.)" by Hillis et al. (1996)
- Frankham, R., Ballou, J. D., Ralls, K., Eldridge, M. D. B., Dudash, M. R., Fenster, C. B., Lacy, R. C. & Sunnucks, P. 2017. Genetic Management of Fragmented Animal and Plant Populations. -xxiii + 401 pp. Oxford University Press, Oxford.
- Futuyma, D. J. & Kirkpatrick, M. 2017. Evolution, 4th ed. -xviii + 602 pp. Sinauer Associates, Inc., Sunderland.
- Hillis, D. M., Moritz, C. & Mable, B. K. 1996. Molecular Systematics, 2nd ed. -xvi + 655 pp. Sinauer Associates, Inc., Sunderland.
- Simpson, M. G. 2006. Plant Systematics. -xi + 590 pp. Elsevier Academic Press, Oxford.