Gene duplication

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Schematic representation of a duplication

Duplicated area :, duplicated section '
Before duplication:, before the duplication'
After duplication:, after the duplication '

In genetics, gene duplication refers to the duplication of a certain section of a chromosome , i.e. the permanent duplication (up to multiplication) of individual genes or gene groups (with subsequent separate development). This type of gene mutation arises, for example, from unequal crossing over either between homologous chromosomes or between sister chromatids . A distinction is made between partial and complete gene duplication. The 2R hypothesis suspects a twofold genome duplication in vertebrates, which led to the various repeated gene clusters and isozymes . This makes the chromosome larger and the DNA matrix longer. The original gene and the gene resulting from its duplication are related to the paralogy , they are paralogous to each other.

As a rule, this mutation cannot be repaired by its own repair mechanisms and often leads to congenital defects due to the serious change in the gene sequence. However, gene duplication is also an essential mechanism of evolution . Functionally new genes can arise through mutations in the gene copy or the spectrum of the original gene activity can be expanded. For example, it was only through the gene duplication of the L- cone that humans became trichromats , which enabled them to perceive colors . Another example is the family of hemoglobins , with different affinities for oxygen . However, pseudogenes can also arise from gene duplications . Numerous gene duplications (e.g. of olfactory receptor genes) are present in the genome of different people in different forms and frequencies and form so-called gene copy number variants .