The end result is two cells that have an extra copy of one chromosome and two cells that are missing that chromosome. Nondisjunction in meiosis I occurs during anaphase I when one pair of homologous chromosomes fails to separate. In this example, one cell with 5 chromosomes and one cell with 3 chromosomes are produced.
Just so, what are some disorders that result from Nondisjunction?
- Down Syndrome. The result of an extra copy of chromosome 21.
- Patau Syndrome. The result of an extra copy of chromosome 13.
- Edward's Syndrome. The result of an extra copy of chromosome 18.
- Nondisjunction Of The Sex Chromosomes.
- Klinefelter Syndrome.
- Trisomy X.
- Monosomy X (Turner's syndrome)
What is nondisjunction and what does it cause?
Karyotype of trisomy 21 (Down syndrome) Note that chromosome 21 is present in 3 copies, while all other chromosomes show the normal diploid state with 2 copies. Most cases of trisomy of chromosome 21 are caused by a nondisjunction event during meiosis I (see text).
What is nondisjunction and what problems does it cause?
Nondisjunction is the failure of homologous chromosomes or chromatids to segregate during mitosis or meiosis. Nondisjunction during mitosis can result in cancer. Nondisjunction during meiosis can cause chromosomal disorders, such as trisomy 21 (Down syndrome), Turner's syndrome, and Klinefelter's syndrome.