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.
Structural chromosomal aberrations involve changes in the structure of one or more chromosomes. These can include:
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.
Duplications involve the presence of extra copies of a chromosome segment. This can lead to an overabundance of specific genes, potentially causing genetic disorders.
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.
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.