How many single gene disorders are there?

The notable. Bcr-abl is a single translocated change in chrinic myelogenous leukemia. The target drug (imatinib, gleevec) controls the mutation, and the disease. Gi stromal tumors, gist, has c-kit managed by the same drug, but resistance occurs. Common cancers are poly-mutated genes. Even brca-1 =2 mutation convey risk in breast and ovarian cancer, not just one gene= cancer.