nondisjunction

(redirected from Chromosomal non-disjunctions)
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Related to Chromosomal non-disjunctions: Meiotic nondisjunction

nondisjunction

 [non″dis-jungk´shun]
failure either of two homologous chromosomes to pass to separate cells during the first meiotic division, or of the two chromatids of a chromosome to pass to separate cells during mitosis or during the second meiotic division. As a result, one daughter cell has two chromosomes or two chromatids, and the other has none. If this happens during meiosis, an aneuploid individual (for example, a child with Down syndrome) may develop following fertilization.
Nondisjunction. Normal meiosis (A) is contrasted with failure of homologous chromosomes to separate in meiosis I (B) or of sister chromatids to separate in meiosis II (C). From Dorland's, 2000.

non·dis·junc·tion

(non'dis-jŭnk'shŭn), [MIM*257300]
Failure of one or more pairs of chromosomes to separate at the meiotic stage of karyokinesis, with the result that both chromosomes are carried to one daughter cell and none to the other.

nondisjunction

/non·dis·junc·tion/ (-dis-junk´shun) failure either of two homologous chromosomes to pass to separate cells during the first meiotic division, or of the two chromatids of a chromosome to pass to separate cells during mitosis or during the second meiotic division. As a result, one daughter cell has two chromosomes or two chromatids, and the other has none.
Enlarge picture
Nondisjunction. Normal meiosis (A) is contrasted with failure of homologous chromosomes to separate in meiosis I (B) or of sister chromatids to separate in meiosis II (C).

nondisjunction

(nŏn′dĭs-jŭngk′shən)
n.
The failure of paired chromosomes or sister chromatids to separate and go to different cells during meiosis.

non′dis·junc′tion·al adj.

nondisjunction

[-disjungk′chən]
Etymology: L, non + disjungere, to disjoint
failure of homologous pairs of chromosomes to separate during the first meiotic division or of the two chromatids of a chromosome to split during anaphase of mitosis or the second meiotic division. The result is an abnormal number of chromosomes in the daughter cells. Compare disjunction. See also monosomy, trisomy.

non·dis·junc·tion

(non'dis-jŭngk'shŭn)
Failure of one or more pairs of chromosomes to separate at the meiotic stage of karyokinesis, with the result that both chromosomes are carried to one daughter cell and none to the other.
Enlarge picture
NONDISJUNCTION

nondisjunction

(nŏn″dĭs-jŭnk′shŭn)
The failure of a pair of chromosomes to separate during meiosis, allowing one daughter cell to have two chromosomes and the other to have none.
See: illustration
Nondisjunctionclick for a larger image
Fig. 230 Nondisjunction . (a) Normal disjunction (b) Nondisjunction.

nondisjunction

the failure of chromosomes (in eukaryotes) to go to opposite poles during nuclear division, leading to unequal numbers of chromosomes in the daughter cells (see ANEUPLOIDY). See Fig. 230 . Nondisjunction produces abnormal numbers of both AUTOSOMES (e.g. DOWN'S SYNDROME) and SEX CHROMOSOMES (e.g. TURNERS SYNDROME).

Nondisjunction

A genetic term referring to an event which takes place during cell division, in which a genetic accident causes an egg or sperm cell to have 24 chromosomes, rather than the normal 23.
Mentioned in: Down Syndrome

nondisjunction

failure (1) of two homologous chromosomes to pass to separate cells during the first division of meiosis, or (2) of the two chromatids of a chromosome to pass to separate cells during mitosis or during the second meiotic division. As a result, one daughter cell has two chromosomes or two chromatids, and the other has none. Death of the fetus or chromosomal anomalies may result.