Due to failure in pairing of homologous chromosomes in meiosis, the two members of one pair migrate to the same pole, giving rise to unbalanced gametes, one of which contain both homologous chromosomes, and the other none (most frequent in sex chromosomes). The non-disjunction event is much more frequent in maternal meiosis I. This may be due to the fact that in a mature woman, oocytes have been held in the ovary for a very long time at prophase I of meiosis from before her birth to shortly before ovulation of the oocyte in question.
Failure of disjunction or separation of homologous chromosomes or chromatids in mitosis or meiosis, resulting in too many chromosomes in some daughter cells and too few in others. Examples: In meiosis, both members of a pair of chromosomes go to one pole so that the other pole does not receive either of them; in mitosis, both sister chromatids go to the same pole.
The failure of a pair of chromosomes to separate during cell division (mitosis), resulting in an abnormal number of chromosomes in the resulting new cells. Non-disjunction of chromosome 21 is the mechanism underlying most cases of Down syndrome.
A failure of chromosome separation in which a pair of chromosomes, or chromatids, pass to one pole of a cell instead of to opposite poles.
The failure of a pair of chromosomes to separate, resulting in an unequal number of ‘daughter’ cells.
When homologous chromosomes fail to segregate properly during meiosis. Down syndrome, Turner syndrome and Klinefelter syndrome result from non-disjunction.
The failure of cell division that leads to chromosomes mis-dividing during meiosis or mitosis leading to the loss or gain of a chromosome or chromosomes.
The failure of a pair of homologous chromosomes to separate properly during meiosis. The failure of homologues (at meiosis) or sister chromatid s (at mitosis) to separate properly to opposite poles, that is two chromosomes or chromatids go to one pole and none to the other.
when chromosomes fail to separate during meiosis such that one gamete gets the diploid number of chromosomes.
The failure of paired chromosomes or sister chromatids to separate and go to different cells during meiosis.