Development of Aneuploids
Phenotypic Effects of Aneuploidy
Development of aneuploids
The development of aneuploids is not well understood, but they may have arisen by a process called non-disjunction. Non-disjunction occurs when paired chromosomes do not separate either during meiosis I or meiosis II. The direct result of this event is that gametes develop that have too few or too many chromosomes. If this occurs during meiosis I normal gametes are not developed, and if it occurs during meiosis II half of the gametes will be normal and the other half will be abnormal.
Non-disjunction can also occur during mitosis and the result is an individual that expresses chromosomal mosaicism. If this occurs during the early stages of cell divisions different portions of the body which descended from the different altered cells. (See figure 19.20.) Many sex chromosome mosaics have been detected for example X/XX, X/XY, XX/XY and XXX/XXXXY. Mild to severe phenotypic symptoms have been associated with these mosaics
. Copyright © 1998. Phillip McClean