APC and colorectal cancer: The aim of our study is to focus on assessing CN for the APC gene in a well- defined group of colorectal cancers, each demonstrating significant LOH of APC. We hypothesized that definite LOH would clearly indicate one allele had been lost, and thus knowing the exact copy number of this critical gene would allow us to test the concept of allele duplication in sporadic colorectal cancer, and lead to a better understanding of the role of APC in colorectal carcinogenesis.