We did observe a slight increase in the total number of replacements per crypt in non-dysplastic FAP colon crypts that carry heterozygous APC mutations, perhaps suggesting that the ‘first-hit’ loss of APC in the development of sporadic colorectal cancer confers a selective advantage, which may help explain why APC mutations are common in colorectal cancers. Here, APC is linked to Familial adenomatous polyposis.