Chromosomal Aberrations: Structural and Numerical Variations

Introduction

Chromosomal aberrations refer to changes in the structure or number of chromosomes, leading to genetic disorders and developmental abnormalities. These variations can be classified into structural and numerical aberrations.

Types of Structural Chromosomal Aberrations

Structural chromosomal aberrations occur due to breaks in chromosomes, leading to rearrangements. These include:

1. Deletions

A portion of the chromosome is lost, leading to missing genetic material. Example: Cri-du-chat syndrome (deletion in chromosome 5).

2. Duplications

A segment of the chromosome is duplicated, resulting in extra genetic material. Example: Charcot-Marie-Tooth disease.

3. Inversions

A chromosome segment is reversed end-to-end, altering gene sequence but usually not causing loss of genetic material.

4. Translocations

Exchange of chromosome segments between non-homologous chromosomes. Example: Chronic Myeloid Leukemia (Philadelphia chromosome).

Types of Numerical Chromosomal Aberrations

Numerical aberrations involve changes in chromosome number, often due to errors in cell division.

1. Aneuploidy

Presence of an abnormal number of chromosomes. Examples:

• Trisomy 21 (Down syndrome) - Extra chromosome 21.
• Turner syndrome - Missing X chromosome in females.

2. Polyploidy

Presence of extra sets of chromosomes, often lethal in humans.

Causes and Diagnosis

Chromosomal aberrations can result from radiation, viral infections, or errors during meiosis. Diagnosis is performed using karyotyping, fluorescence in situ hybridization (FISH), and chromosomal microarray analysis.

Conclusion

Understanding chromosomal aberrations is crucial for diagnosing genetic disorders and developing therapeutic interventions. Advances in genetic research continue to improve detection and treatment strategies.