Biallelic expression of CCND1 alleles in D1 group of MM tumors. Paired genomic DNA and cDNA samples were used to PCR amplify 138-bp exon 4-intron 4 or, respectively, 203-bp exon 4-exon 5 DNA fragments that include an A>G polymorphism at the ultimate exon 4 nucleotide. (A) The resultant fragments were digested with HpaII, which generates 92 + 46-bp fragments or, respectively, 161 + 42-bp fragments when a G is present at the polymorphic site. Paired HpaII-digested samples were subjected to electrophoresis on a 4% Nusieve-0.5% agarose gel. Odd lanes contain genomic fragments; subsequent even lanes contain the corresponding cDNA fragment. Lanes 1-2, homozygous A allele; lanes 3-4, homozygous G allele; lanes 5-22, 9 MM tumor samples. The positions of the 203-bp, 161-bp, 138-bp, and 92-bp fragments are indicated at the left. (B) Paired sequence tracings of genomic and cDNA fragments from representative tumors that have an excess of the A allele (dotted lines), the G allele (solid lines), or equal representation of both alleles. The polymorphic A>G nucleotide and the subsequent G nucleotide are shown. Further details in “Patients, materials, and methods.”