A term originally devised by Hugo M. de Vries (1848-1935) in 1901, it refers to a random alteration in the arrangement or amount of genetic material in a cell that may cause it and all cells derived from it to differ in structure and function. An organism affected by a mutation is called a mutant. There are two general types of mutations: point mutations consisting of minor changes in the genetic material such a single-base pair substitutions in structural genes and macro mutations involving larger sections of chromosomes. There are five specific types of macro mutations as shown in the figure below. Mutations most often occur during DNA replication when so-called ‘copying errors’ can arise. More often than not, mutations are lethal, but sometimes they can be advantageous given particular environmental circumstances in the sense of increasing the chances of survival and reproductive success.
