Haploinsufficiency

Haploinsufficiency is a term used in genetics. The haploinsufficiency denotes a diploid ( "double " ) gene, which can not effect the normal phenotype in the haploid ( "half" ) state. Haploinsufficiency is an example of how the dominance of a disease-causing allele is established.

Each diploid organism has on its homologous chromosomes, two copies of a gene. If a copy of an inherited mutation has become inoperable and the non (usually a protein ) results in a functioning copy of the gene producing a sufficient amount of the gene product, as occurs in the genetic disease. A single mutant allele is therefore sufficient, in order to stamp out the disease, it ill also heterozygous, ie heterozygous, carrier of hereditary disease.

For proteins that are present in the organism as oligomers, is that missense or nonsense mutations on one allele may occur and may lead to inactive oligomers. So the functionality preserved alleles is reduced dramatically. An example is the tumor suppressor gene p53, which is connected ( in addition to its importance for many tumors) with the Li -Fraumeni syndrome.

Also favor mutants on one allele, the same mutation in the second allele of a mitotic recombination, or by a copy choice of DNA replication. These variants cause spontaneous mutations in addition to a loss of heterozygosity and can lead to cancer. Among these was, for example, the hereditary bilateral retinoblastoma or familial adenomatous polyposis.

In contrast, the disease in only homozygous recessive disorders, so true-breeding, gene carriers.

Other examples of human genetic disorders that are based on haploinsufficiency are:

• Chondrodysplasia
• Huntington's disease
• Polydactyly
• Marfan syndrome