Chromosomal Aberrations

Chromosomal Aberration

- Chromosomal aberrations are genetic abnormalities that involve alterations in the structure or number of chromosomes within an organism's cells.

- These aberrations can have significant effects on an individual's phenotype and can lead to various genetic disorders. 

1. Numerical Aberrations:

Numerical aberrations involve changes in the total number of chromosomes in a cell. There are two primary categories:

 

a. Aneuploidy:

- Aneuploidy occurs when there is an abnormal number of chromosomes in a cell due to errors in chromosome segregation during cell division.

- Examples of aneuploidy:

Trisomy: An extra chromosome is present (e.g., Down syndrome, caused by trisomy 21).

Monosomy: One chromosome in a pair is missing (e.g., Turner syndrome, caused by monosomy of the X chromosome in females).

  b. Polyploidy:

- Polyploidy is characterized by the presence of extra sets of chromosomes beyond the typical diploid number (2n).

- Polyploidy can lead to triploid (3n), tetraploid (4n), or higher ploidy levels.

- It is more common in plants and less frequent in animals.

 2. Structural Aberrations:

Structural chromosomal aberrations involve changes in the structure of one or more chromosomes. These can include:

 a. Deletions:

Deletions occur when a segment of a chromosome is missing or deleted. This loss of genetic material can result in developmental abnormalities or genetic disorders.

 b. Duplications:

Duplications involve the presence of extra copies of a chromosome segment. This can lead to an overabundance of specific genes, potentially causing genetic disorders.

 c. Inversions:

Inversions happen when a chromosome segment breaks off, flips, and reattaches in the reverse orientation. Inversions can disrupt gene function if they occur within coding regions.

 d. Translocations:

Translocations entail the exchange of chromosome segments between non-homologous chromosomes. This can lead to a rearrangement of genetic material and may result in genetic disorders.