Mutations

Mutations are local changes in the DNA content, caused by inexact replication. Mutations occur often due to radiation and other environmental conditions. Substitution occurs when one base is replaced by another. Insertion and deletion are the addition and removal of one or more bases, respectively. Substitution, as well as insertion or deletion of a single base is called point mutation. A rearrangement is a change in the order of complete segments along a chromosome. Mutations are important to us for several reasons. They are responsible for inherited disorders and other diseases such as cancer, that involve alterations in the genes. At the same time, mutations are the source of phenotypic variation on which natural selection acts, creating speciesand changing them. For example, the human and the mice genomes are very similar. The major difference between them is the internal order of DNA segments. A complex problem that arises is: