Variations within the DNA sequence of a particular gene affect its function, and may cause or predispose an individual a particular disease. Alterations in the genome may increase the frequency of disorder and disease with entire populations.

Although there are many types of genetic disorders, a specific disorder does not have to be inheritable to have a genetic basis. For example, non-heritable disorders can also arise from mutations in somatic cells resulting from exposure to mutagenic factors in the environment. Mutations, whether inherited mutations that appear in every cell of the body, or random mutations affecting a particular cell, can cause groups of cells to grow out of control, or inhibit the processes (contact inhibition processes) that normally prevent this from happening.

Some diseases and disorders are traced to the presence of a single form of a gene, to a mutation in...