Hereditary Function of DNA

To geneticists, the arrangement of bases in a DNA molecule spells out a "language" known as the genetic code. A sequence of three specific bases forms the code for one amino acid in a protein. Since DNA contains four different bases, each of which occurs thousands of times in human cells, the number of possible different arrangements of these bases is astronomically high. This makes possible the wide diversity that exists in the genetic makeup of human beings. At conception, the characteristics of the offspring are determined by the arrangement of bases in the DNA of the parents.

A mutation (an alteration in the DNA) in the gametes of either parent is sufficient to cause a noticeable change in the offspring. Such alterations can be caused by radiation from such sources as cosmic rays and nuclear explosions.