Karyotyping is a laboratory technique used in cytogenetics to examine the number
Karyotyping is a laboratory technique used in cytogenetics to examine the number, size, shape, and structure of chromosomes in an individual's cells. It provides a visual representation of the chromosome complement, known as the karyotype, which is essential for identifying chromosomal abnormalities such as aneuploidy (incorrect chromosome number), structural variations (such as translocations, deletions, or inversions), and other genetic disorders.
Process of Karyotyping:
- Sample Collection: Cells are usually obtained from blood, bone marrow, amniotic fluid, or a biopsy.
- Cell Culture: If needed, cells are cultured to promote division, as chromosomes are most visible during mitosis, specifically in the metaphase stage.
- Chromosome Preparation: The cells are treated with chemicals to halt cell division at metaphase. The cells are then fixed, stained, and spread onto a slide.
- Microscopic Examination: The stained chromosomes are viewed under a microscope, where they are photographed and arranged in a standardized way. The chromosomes are grouped by size, centromere position, and banding patterns.
- Karyotype Analysis: The image is analyzed for:
- Chromosome Number: Normal human cells have 46 chromosomes, arranged in 23 pairs. An abnormal number indicates conditions like Down syndrome (trisomy 21, 47 chromosomes).
- Chromosomal Structure: Structural anomalies, such as deletions (missing pieces), duplications, inversions, or translocations, can also be identified.
Uses of Karyotyping:
- Prenatal Screening: Detects genetic disorders in fetuses, such as Down syndrome or trisomy 18.
- Infertility Investigations: Helps identify chromosomal abnormalities that may contribute to infertility or miscarriage.
- Cancer Diagnosis: Certain cancers are associated with chromosomal changes, such as Philadelphia chromosome in chronic myelogenous leukemia (CML).
- Genetic Counseling: Assists in understanding genetic risks and providing advice to families.
Karyotyping is a crucial tool for identifying chromosomal abnormalities that might not be detected through other genetic tests. However, newer techniques like fluorescence in situ hybridization (FISH) and chromosomal microarray are sometimes used for more detailed analysis.
