colo 320 cells carrying homogeneously staining chromosomal regions have 15 to 20 copies of an apparently normal c-myc allele and 1 to 2 copies of an abnormal c-myc allele lacking exon 1 and express high levels of a normal c-myc mrna 2.5 kilobases in size .
C0007634
cells
C0015295
exon