Complex heterozygosity
Complex heterozygosity is a term used in genetics . It is used in two different meanings.
a) Complex heterozygous is a form of heterozygous in which only individuals with heterozygous genetic material that has various translocation complexes are viable . These arise when several chromosomes have exchanged whole chromosome arms for one another (whole arm reciprocal translocation, WART). Since every single chromosome no longer has a homologous partner in meiosis , gametes can now only be formed if different chromosomes connect one arm to the homologous arm of another chromosome. This different pairing creates a ring structure in which several chromosomes come together to form a ring, so that ultimately each arm finds a homologous partner. The heterozygous form is thus viable, while the homozygous form cannot form viable gametes in meiosis. A recombination at meiosis is rare, but possible, the complexes involved can be changed. Complex heterozygosity has only been demonstrated in a few species. It is best known in the evening primrose (genus Oenothera ), where it was created several times by interspecific hybridization of two homozygous species. Another species is the wood shrew ( Sorex araneus ), in which several chromosome races can be distinguished, each with complex-heterozygous inheritance.
b) Combined, mixed or complex heterozygosity (also after the English compound heterozygote: compound heterozygosity ) occurs when both alleles of a recessive inherited disease carry a mutation that is different and causes the disease at the same gene locus . As a result, two disease-causing gene variants (alleles) occur in one and the same person, one of which is normally inherited from the mother and one from the father. For example, the autosomal recessive inherited cystic fibrosis is often based on two different mutations of the CFTR gene ( Cystic Fibrosis Transmembrane Conductance Regulator ) present on the long arm of human chromosome 7 (see also ΔF508 mutation).
Individual evidence
- ^ A b Sydney Brenner, Jeffrey Miller: Brenner's Encyclopedia of Genetics. Springer Verlag, 2nd edition 2013, ISBN 978-0-12-374984-0 .
- ^ Robert C. King, William D. Stansfield, Pamela K. Mulligan: A dictionary of genetics. Oxford University Press, 7th edition, 2006 ISBN 978-0-19-530762-7 .