nondisjunction
Sign in to save600px|thumb| The left image at the blue arrow is nondisjunction taking place during meiosis II. The right image at the green arrow is nondisjunction taking place during meiosis I. Nondisjunction is when chromosomes fail to separate normally resulting in a gain or loss of chromosomes. Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division (mitosis/meiosis). There are three forms of nondisjunction: failure of a pair of homologous chromosomes to separate in meiosis I, failure of sister chromatids to separate during meiosis II, and fa
Article
27 sectionsContents
- Types
- Meiosis II
- Mitosis
- Molecular mechanisms
- Central role of the spindle assembly checkpoint
- Sex-specific differences in meiosis
- Age-related loss of cohesin ties
- Consequences
- Monosomy
- Turner syndrome (X monosomy) (45, X0)
- Autosomal trisomy
- Down syndrome (trisomy 21)
- Edwards syndrome (trisomy 18) and Patau syndrome (trisomy 13)
- Sex chromosome aneuploidy
- Klinefelter syndrome (47, XXY)
- XYY Male (47, XYY)
- Trisomy X (47,XXX)
- Uniparental disomy
- Mosaicism syndromes
- Mosaicism in malignant transformation
- Diagnosis
- Preimplantation genetic diagnosis
- Karyotyping
- Polar body diagnosis
- Blastomere biopsy
- Lifestyle/environmental hazards
- References
600px|thumb| The left image at the blue arrow is nondisjunction taking place during meiosis II. The right image at the green arrow is nondisjunction taking place during meiosis I. Nondisjunction is when chromosomes fail to separate normally resulting in a gain or loss of chromosomes. Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division (mitosis/meiosis). There are three forms of nondisjunction: failure of a pair of homologous chromosomes to separate in meiosis I, failure of sister chromatids to separate during meiosis II, and failure of sister chromatids to separate during mitosis. Nondisjunction results in daughter cells with abnormal chromosome numbers (aneuploidy).
Calvin Bridges and Thomas Hunt Morgan are credited with discovering nondisjunction in Drosophila melanogaster sex chromosomes in the spring of 1910, while working in the Zoological Laboratory of Columbia University. Proof of the chromosome theory of heredity emerged from these early studies of chromosome non-disjunction.