Nondisjunction is a type of chromosomal mutation that occurs during cell division, specifically during meiosis or mitosis. It happens when chromosomes fail to separate properly, leading to an abnormal distribution of chromosomes in the daughter cells.
During normal cell division, chromosomes are supposed to separate evenly into two daughter cells. However, in the case of nondisjunction, the chromosomes do not separate as they should. This can result in one daughter cell receiving an extra chromosome (trisomy) and the other daughter cell missing a chromosome (monosomy).
Nondisjunction can lead to various genetic disorders. For example, Down syndrome is caused by an extra copy of chromosome 21 due to nondisjunction. Similarly, Turner syndrome and Klinefelter syndrome are also results of nondisjunction.
In summary, nondisjunction is a chromosomal mutation that occurs when chromosomes fail to separate properly during cell division, leading to an abnormal number of chromosomes in the resulting cells.