Principles of Biochemistry Volume 3 - A. Lehninger 1985

Molecular Mechanisms of Genetic Information Transfer
More About Genes: Repair, Mutation, Recombination, and Cloning
Mutations are random, rare events in the lives of individuals

Mutations in the real life of an individual Organism are extremely rare events. The probability of a mutation occurring during the lifetime of a single E. coli Cell is 10^-9. For a human cell, this probability is higher—on the order of 10^-5; this value was calculated based on the incidence of hemophilia, a genetic disease rooted in impaired Blood clotting mechanisms that leads to prolonged bleeding. Hemophilia was one of the first human hereditary disorders whose nature was successfully understood. A classic example of this condition is hemophilia in the family of Queen Victoria of England, which has been traced through three generations of her descendants belonging to the royal families of England, Prussia, Spain, Greece, and Russia. In humans, along with "silent," harmless, or beneficial mutations that cause no complications, there can be mutations leading to genetically inherited disorders manifested by impairments in normal bodily Functions. To date, mutations in approximately 2,500 different genes have been identified in humans; many of these either impair certain functions or ultimately prove fatal. The remaining mutable human genes have yet to be discovered. Evidently, the number of identified human Hereditary diseases will grow with the advent of Methods capable of detecting the consequences of mutations. Hereditary diseases pose an exceptionally important challenge for Biochemistry and Medicine regarding their Diagnosis and Treatment.