When aneuploidy is detected in a fraction of cells in an individual, it is called chromosomal mosaicism. In general, individuals who are mosaic for a chromosomal aneuploidy tend to have a less severe form of the syndrome compared to those with full trisomy. For many of the autosomal trisomies, only mosaic cases survive to term. However, mitotic aneuploidy may be more common than previously recognized in somatic tissues, and aneuploidy is a characteristic of many types of tumorigenesis (see below). Mechanisms
Aneuploidy arises from errors in chromosome segregation, which can go wrong in several ways.Nondisjunction usually occurs as the result of a weakened mitotic checkpoint, as these checkpoints tend to arrest or delay cell division until all components of the cell are ready to enter the next phase. For example, if a checkpoint is weakened, the cell may fail to notice that a chromosome pair is not lined with the spindle apparatus. In such a case, most chromosomes would separate normally (with one chromatid ending up in each cell), while others could fail to separate at all. This would generate a daughter cell lacking a copy and a daughter cell with an extra copy.Completely inactive mitotic checkpoints may cause nondisjunction at multiple chromosomes, possibly all. Such a scenario could result in each daughter cell possessing a disjoint set of genetic material.Merotelic attachment occurs when one kinetochore is attached to both mitotic spindle poles. One daughter cell would have a normal complement of chromosomes; the second would lack one.
It has since aired on Discovery Fit & Health in the United States.Danielle Falan, from São Paulo, Brazil, is one of the oldest surviving people with MOMO syndrome. At age 17 she was featured in the Archie Thompson documentary as her mother traveled to visit her in Brazil. Falan attended school as normal, and hopes to attend college.Six other cases have been diagnosed, in Italy, in Brazil [1], two in Germany,, in Cuba, 2018 Diorkeblin Hernández Durruthy [2] [3], and in Poland. An additional case was reported in 2010. References


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