A chromosomal aberration (or mutation) occurs when any defect occurs to chromosomes or part of them.

Types of Chromosomal Aberrations

There are two types of chromosomal aberrations

  1. Numerical Aberrations
  2. Structural Aberrations

Numerical aberrations

Abnormalities that involve a change in the number of chromosomes but not in the structural or physical appearance of the chromosomes. Numerical aberrations are caused by nondisjunction (failure of homologous chromosomes or sister chromatids to separate properly during cell division) either during meiosis I, meiosis II OR mitosis.

Non-disjunction in Mitosis (Credit; Alex Federspiel, CC BY-SA 4.0)
Non-disjunction in Meiosis II( for the first picture) and Meiosis I(for the second picture). (Credit; Tweety207,CC BY-SA 3.0)

Numerical aberrations can be euploidy or aneuploidy.

  • Euploidy: is the state of a cell or organism having more than one set of chromosomes. The

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