In contrast, almost all changes of copy number at the Trp53 gene in tumours from Trp53ΔP mice were seen in 56Fe-ion radiation-exposed animals (Fig. 7c), suggesting that focal DNA damage of the type induced by heavy ions is more likely to result in loss of Trp53 in mice with this mutant allele, which is known to retain some residual Trp53 function28. Here, TP53 is linked to neoplasm.