In Reply We agree with Dr Casola that we may have misused the term allele in reference to the additional elephant TP53 (ep53) genes. We also agree, as highlighted in our article, that the exact role of ep53 remains to be determined. Ep53 appears to originate from ancient reverse transcription of TP53 mRNA, followed by a large number of gene duplications. A retrotransposed gene can still encode a protein even if not identical to the ancestral protein, as indicated by our experiments with ep53 retrogene 9. It is unclear if the additional ep53 genes should be called retrogenes or retropseudogenes. Laboratory experiments to answer these questions are ongoing.
Schiffman JD, Schmitt DL, Maley CC. TP53 Gene and Cancer Resistance in Elephants—Reply. JAMA. 2016;315(16):1790-1791. doi:10.1001/jama.2016.0457