Uniparental disomy
In a uniparental disomy (UPD), both chromosomes of a homologous chromosome pair come from one parent. Diploid organisms, which include all mammals, usually receive a complete set of chromosomes from the father and one from the mother. In uniparental disomy, however, both chromosomes of a chromosome pair come from the same parent.
The phenomenon became known because a uniparental disomy of chromosome 15 in humans causes Prader-Willi syndrome (with maternal disomy) or Angelman syndrome (with paternal disomy). By imprinting (embossing) , an area is marked on this chromosome differently in the germ line of mother and father. As a result, the areas on the maternal and paternal chromosomes are read differently during the child's development. In the case of a disomy, part of the normal expression is therefore missing, so that the syndromes mentioned occur.
A uniparental disomy also occurs in a special form of pseudohypoparathyroidism type 1b, with chromosome 20 with the alpha subunit of the G protein-coupled receptor of the parathyroid hormone being affected.
The most common cause of the development of UPD is suspected to be a double presence of a chromosome in the egg , which leads to a trisomal zygote. Correcting the trisomy can result in a disome embryo. If both chromosomes of one parent are passed on, it is called heterodisomy . If the same chromosome is present twice, this is called isodisomy (alleles identical).
The diagnosis can be made using microsatellite markers on the suspected chromosome or gene segment.
See also
Individual evidence
- ↑ Ryan W. Carroll, Michelle L. Katz, Elahna Paul, Harald Jüppner: Case 17-2017 - A 14-Year-Old Boy with Acute Fear of Choking while Swallowing , New England Journal of Medicine 2017, Issue 376 of June 8th 2017, pages 2266-2275; DOI: 10.1056 / NEJMcpc1616019 (case description of a 14-year-old boy with pseudohypoparathyroidism type 1b)