Mutation is an alteration in an organism's genes. The mutation is carried to the organism's offspring, so the offspring may look or act different from its ancestors. Mutations may be beneficial or harmful, or they may have no noticeable effect at all. Genes consist of long strings of DNA molecules. DNA takes the form of a spiral ladder, with rungs made of two interlocking substances called bases. The sequence of the rungs of the DNA ladder determines the genetic code of the organism. Any change or break in the DNA ladder alters the genetic code, and so makes a change in the next generation of the organism, whether it is a bacterium or a human being.

The discovery and naming of mutation is credited to a Dutch botanist, Hugo De Vries. He studied the evening primrose flower, and actually came up independently with the same laws of genetics...