Human genetic polymorphisms

Mutations in the human genome lead to genetic polymorphisms in the population. While many of these are considered to be normal variants, many lead to human disease and are usually maintained in the population by a balance between mutation and selection. The frequency and type of mutations have been determined for a number of loci in man. The frequency of mutation in transgenes is now receiving considerable attention, since proteins synthesized in recombinant DNA biological systems are subject to genetic alteration through mutation and selection. These changes can occur in the transgene, but mutations in the host cell genes can also produce structural modifications for example, by changes in post-translational modification. Mutation rates for human genes may be as high as 10(-5) per locus per generation. Spontaneous mutations that inactivate gene function in bacteria occur at a rate of 10(-5)-10(-6) per locus per generation. On the other hand the frequency of spontaneous mutations per nucleotide is two orders of magnitude less (usually less than 10(-7)).