Work on many disease genes, including the breast cancer gene BRCA1, the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR), the growth hormone gene GH1 and the ataxia telangiectasia mutated gene ATM, has demonstrated that all classes of point mutations, including nonsense mutations, can disrupt exonic splicing regulatory elements (ESRs) and induce aberrant pre-mRNA splicing [2-6]. The gene discussed is GH1; the disease is breast carcinoma.