Hypermutation at the immunoglobulin heavy chain locus in a pre-B-cell line.

Abstract
Most cells in the well-known pre-B-lymphocyte line 18-81 have correctly assembled genes for both alleles at the Ig heavy chain locus. Only one allele is active; the other, silent allele contains an amber termination codon. The rate of reversion of this amber codon was determined to be 0.3-1 .times. 10-4 per cell generation. This high rate is termed hypermutation.