Notes: The authors studied the loss of heterozygosity (LOH) at the APC locus 1638N in mouse intestinal tumors. The entire intestinal tract was removed from 85–95-day-old B6 mice heterozygous for 1638N. The tumors present were dissected out and frozen in liquid nitrogen before DNA was isolated using the Tissue and Hair Extraction Kit with the DNA IQ™ System. To determine the allele ratio, 35ng DNA was amplified in a 12.25µl amplification reaction using 1 unit Taq DNA Polymerase and a radiolabeled nucleotide. The amplification products were then separated on a 6% acrylamide gel and analyzed by phosphorimaging. (3098)