You asked: What is nondisjunction of chromosomes during cell division?

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division.

What is nondisjunction and when does it occur?


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 the nondisjunction during 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.

What are some examples of nondisjunction?

Examples of nondisjunction:

  • Down syndrome.
  • Triple-X syndrome.
  • Klinefelter’s Syndrome.
  • Turner’s Syndrome.

What is the effect of nondisjunction in the daughter cells?

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.

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What are the results of nondisjunction?

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?

During anaphase of the cell cycle, chromosomes are separated to opposite ends of the cell to create two daughter cells. Nondisjunction is the failure of the chromosomes to separate, which produces daughter cells with abnormal numbers of chromosomes. [

Which trait is found in the body chromosomes are also known as autosomes?

An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosome pairs which may have different structures. The DNA in autosomes is collectively known as atDNA or auDNA.


Karyotype of human chromosomes
Female (XX) Male (XY)

How do nondisjunction errors in meiosis lead to aneuploidies such as trisomies and Monosomies?

Aneuploidy is caused by nondisjunction, which occurs when pairs of homologous chromosomes or sister chromatids fail to separate during meiosis. The loss of a single chromosome from a diploid genome is called monosomy (2n-1), while the gain of one chromosome is called trisomy (2n+1).

Is Patau syndrome genetic?

Patau’s syndrome is a serious rare genetic disorder caused by having an additional copy of chromosome 13 in some or all of the body’s cells. It’s also called trisomy 13.

What chromosome is Down syndrome?

Babies with Down syndrome have an extra copy of one of these chromosomes, chromosome 21. A medical term for having an extra copy of a chromosome is ‘trisomy. ‘ Down syndrome is also referred to as Trisomy 21.

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What is the difference between aneuploidy and Euploidy?

Euploidy refers to the change in the complete set of chromosomes, i.e. loss or gain of the full set of chromosomes. … Aneuploidy refers to the gain and loss of one or two chromosomes, e.g. monosomy (2n-1), trisomy (2n+1), nullisomy (2n-2).

Why is nondisjunction more common in older females?

One explanation for why meiotic segregation errors are more prevalent in older women is that cohesion between sister chromatids deteriorates with age and renders recombinant chromosomes susceptible to missegregation.

Which process would cause nondisjunction if it occurred during meiosis?

Figure 7.8 Following meiosis, each gamete has one copy of each chromosome. Nondisjunction occurs when homologous chromosomes (meiosis I) or sister chromatids (meiosis II) fail to separate during meiosis.

What is the result of nondisjunction which results in an extra chromosome in the cell nucleus?


Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate. As the embryo develops, the extra chromosome is replicated in every cell of the body. This type of Down syndrome, which accounts for 95% of cases, is called trisomy 21.