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Chromosomal Mutations


What is a mutation?

      Changes in the genetic material (DNA).

There are two types of mutations that can occur in gamete cells:

1.    Gene mutation: affect only one gene. Examples: point and frameshift.

2.    Chromosomal mutation: affect the number or structure of  chromosomes. Usually involves many, many genes.

5 types of Chromosomal Mutations:

1. Deletion

2.  Duplication

3. Inversion

4. Translocation

5. Non-disjunction

Deletion: Involves the loss of all or part of a chromosome.


Examples: Cri du Chat syndrome, Angelman’s syndrome, Prader-Willi syndrome, Miller-Dieker syndrome

Duplication: Involves the production of extra copies of parts of the chromosome

Examples: Fragile X syndrome, Beckwith-Wiedeman syndrome

Inversion: Reverses the direction of parts of a chromosome.

Translocation: When one part of a chromosome breaks off and attaches to another chromosome.

Example: Edward’s syndrome


      Means “not coming apart”.

      When  homologous chromosomes fail to separate properly during meiosis.


      Results in abnormal numbers of chromosomes. Normal is two of each type of chromosome.

      Trisomy means a person has an extra copy of a chromosome.


      Monosomy means a person is missing a copy of a chromosome.


Examples of Trisomy: Down syndrome, Trisomy 13, Cat eye syndrome (tetrasomy), Klineflelter’s syndrome


Example of Monosomy: Turner’s syndrome