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To the Editor Dr Abegglen and colleagues proposed that the occurrence of multiple copies of the TP53 gene in elephants may be an evolutionary innovation associated with cancer resistance in pachyderms.1 These extra TP53 copies have been described as alleles of the “ancestral” TP53 gene. However, according to the Genetics Home Reference curated by the US National Library of Medicine, the word allele refers to “one of the alternative versions of a gene at a given location (locus) along a chromosome.”2 Copies of a given gene, such as the multiple TP53 copies found in elephants, should be referred to as paralogous genes, or paralogs.3 Alleles represent the range of biological variation of a gene in a species, including deleterious alleles responsible for mendelian disorders, whereas most paralogs perform separate biological functions, are expressed in different tissues or at different developmental stages (for example, the genes encoding globin proteins4), or both. Therefore, suggesting that African elephants possess “40 TP53 alleles”1 is not only semantically incorrect but also biologically inaccurate.
Casola C. TP53 Gene and Cancer Resistance in Elephants. JAMA. 2016;315(16):1788-1789. doi:10.1001/jama.2016.0440