What occurs in a nondisjunction mutation?
Nondisjunction: Failure of paired chromosomes to separate (to disjoin) during cell division, so that both chromosomes go to one daughter cell and none go to the other. Nondisjunction causes errors in chromosome number, such as trisomy 21 (Down syndrome) and monosomy X (Turner syndrome).
What is nondisjunction and during which phases of meiosis can it occur?
When nondisjunction occurs during meiosis, it can happen during anaphase I or anaphase II. When it occurs during anaphase I (as seen in the diagram below, on the right), the homologous chromosomes do not separate. The cells then go through meiosis II normally, resulting in four possible cells.
What is the outcome of nondisjunction in meiosis I quizlet?
Nondisjunction in meiosis I results from failure of homologs to separate; the gametes produced are either n+1 or N-1.
What is nondisjunction in mitosis?
Nondisjunction, in which chromosomes fail to separate equally, can occur in meiosis I (first row), meiosis II (second row), and mitosis (third row). These unequal separations can produce daughter cells with unexpected chromosome numbers, called aneuploids.
Why does nondisjunction of chromosomes cause problems?
Nondisjunction in meiosis can result in pregnancy loss or birth of a child with an extra chromosome in all cells, whereas nondisjunction in mitosis will result in mosaicism with two or more cell lines. Aneuploidy may also result from anaphase lag.
What is nondisjunction in meiosis?
Nondisjunction means that a pair of homologous chromosomes has failed to separate or segregate at anaphase so that both chromosomes of the pair pass to the same daughter cell. This probably occurs most commonly in meiosis, but it may occur in mitosis to produce a mosaic individual.
What is a nondisjunction quizlet?
Nondisjunction refers to the failure of pairs of chromosomes or sister chromatids to separate during meiosis or mitosis.