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The failure of paired chromosomes or sister chromatids to separate and go to different cells during meiosis.

non′dis·junc′tion·al adj.


(Genetics) the failure of paired homologous chromosomes to move to opposite poles of the cell during meiosis
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Noun1.nondisjunction - meiosis in which there is a failure of paired homologous chromosomes to separate; results in an abnormal number of chromosomes in the daughter cells
meiosis, miosis, reduction division - (genetics) cell division that produces reproductive cells in sexually reproducing organisms; the nucleus divides into four nuclei each containing half the chromosome number (leading to gametes in animals and spores in plants)
References in periodicals archive ?
Males occur at a very low frequency (1%) because of nondisjunction of the two X-chromosomes (1X/2A) during meiosis (Nigon 1949b, cited by Haag 2005).
2016), as Bs are also called selfish entities, derived from As, and retain a polymorphism by a series of accumulation mechanisms such as nondisjunction, preferential fertilization, and enhanced pollen transmission (Chiavarino et al.
Based on the common mechanism for tetrasomy 18p,[sup][2] we suspect that the mosaicism of 47, XX,+18/46, XX of the patient is first developed from nondisjunction event in an early mitosis after the formation of the zygote.
Because XXY trisomies frequently arise from nondisjunction of the XY (paternal) bivalent during meiosis I, and increases in XXX trisomy (predominately maternally derived) have not been observed, underlying environmental causes affecting nondisjunction during spermatogenesis are suspected.
Extra chromosome is often maternal and occurs because of meiotic nondisjunction.
sup][2] Trisomy 21 is characterized by the presence of three copies of chromosomes 21, generally resulting from nondisjunction during maternal meiosis whereas the extra chromosome 21 in mosaic DS arises from mitotic nondisjunction in a chromosomally normal zygote.
The molecular analysis of fetus and parents revealed that the extra haploid set of chromosome in fetus is resulted from nondisjunction at maternal meiosis-I.
Greater than 95% of cases are secondary to chromosomal nondisjunction.
Trichlorfon-induced polyploidy and nondisjunction in mouse oocytes from preantral follicle culture.
These include nondisjunction, translocation, and mosaicism.
MN test provides a measure of both chromosome breakage and chromosome loss or nondisjunction in clastogenic and aneugenic events (13).
Tobacco smoke exposure may harm game-to-genesis by adversely affecting chromosomes and damaging the meiotic spindle and has been associated with an increased risk of trisomy 21 offspring resulting from maternal nondisjunction.