Gene duplication
An extra copy of a gene.
Gene duplication is a key mechanism in evolution.
Once a gene is duplicated, the identical genes can undergo changes and diverge to create two different genes.
A duplication is the opposite of a deletion.</P> Duplications typically arise from an event termed unequal crossing-over (recombination) that occurs between misaligned homologous chromosomes during meiosis (germ cell formation).
The chance of this event happening is a function of the degree of sharing of repetitive elements between two chromosomes.
The recombination products of such an event are a duplication at the site of the exchange and a reciprocal deletion.
A remarkable class of duplications in which the duplicated region has popped up far away from home base has also been discovered.