FIGURE 3
Analysis of APC second allele in adenomas. Loss of the mutant allele in an adenoma from a patient carrying mutation on codon 842. A, DNA sequence analysis of the region of exon 15 that contains the germline mutation 2523–2524 insA from lymphocytes. B, from adenomatous cells of the same patient. The bottom chromatograph shows only the remaining normal sequence because the mutant allele has been lost. C, allelic loss detected by polymorphism on exon 15N in two adenomas associated with MT-1383. Lane 1, DNA 100-bp molecular weight marker with band sizes of 300 bp and 600 bp indicated by arrows. Lane 2, germline DNA sample carrying MT-1383. Lanes 3 and 4, DNA samples from two different paraffin-embedded adenomas associated to MT-1383. All samples were amplified, digested by SspI, and run on a 2% agarose gel. The sample in Lane 3 shows a marked LOH, whereas the sample in Lane 4 displays an allelic retention. The greater efficiency of amplification from lymphocyte DNA in respect to DNA extracted from paraffin–embedded adenomas results in a shift and in more intensity of the two bands of the germ-line sample.
