Describe non disjunction and the effect it can have on a human

Describe non disjunction and the effect it can have on a human


There are three forms of non dis junction: failure of a pair of homologous chromosomes to separate in meiosis I, failure of sister chromatids to separate during meiosis II, and failure of sister chromatids to separate during mitosis. Nondisjunction results in daughter cells with abnormal chromosome numbers (aneuploidy). In the sex chromosomes of a cell, nondisjunction can cause some lesser-known diseases, such as Klinefelter syndrome (a male with 2X and 1 Y), Turner syndrome (a female with only one X chromosome), or Trisomy X (female with 3 X chromosomes instead of 2). Hope this helped. 😀

Meiosis is a type of cell division by which chromosome number is reduced to half. It occurs during gamete formation. However, during anaphase I, a pair of chromosome fails to separate or during anaphase II sister chromatids fail to separate during anaphase II of meiosis. Both the cases results into nondisjunction of chromosomes. Nondisjunction forms abnormal number of chromosomes in the gametes.  

Nondisjunction causes human disorders in autosomes from chromosomes 1-22. The examples are Down syndrome or trisomy 21, an extra copy of chromosome 21. People with Down syndrome have 47 chromosome instead 46.  

Nondisjunction can lead to losing chromosomes. It can lead to a condition called monosomy.


Nondisjunction is the improper segregation of chromosomes during either meiotic or mitotic cell division.

The result of nondisjunction is dosage imbalance - either one extra or one missing chromosome for some proportion of the resulting cells.

Nondisjunction in meiosis, occurs during anaphase. When one pair of homologous chromosomes fails to separate. This effects age development and genetic recombination for humans. 

non-disjunction is a pathological event that occurs during the second anaphase in meiosis when sister chromatids are not separated. As a result one of the resulting cells will have 1 extra chromosome and the other will be 1 short. An example of a non-disjunction that can occur in humans is Down syndrome that has a frequency of about 1/1000 people. It is caused by the non-disjunction of the 21st pair of chromosomes.

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