How does karyotyping examine a person’s chromosomes?

Karyotyping is a genetic test used to visualize a person’s complete set of chromosomes to identify structural or numerical abnormalities.12

The process involves several key steps:

• Sample Collection: Living cells are obtained from sources such as blood, skin, bone marrow, or prenatal tissues like the placenta.12
• Cell Culture and Isolation: Technicians grow these cells in tissue culture media. The chromosomes are isolated during metaphase of mitosis, the stage where they are most coiled, condensed, and visible.12
• Staining and Sorting: The chromosomes are stained to produce distinct light and dark bands, which help in their identification. They are then arranged numerically according to a standard classification scheme.12

Once organized, the chromosomes are counted and examined for aberrations such as aneuploidy (atypical number) or structural changes like deletions, duplications, inversions, and translocations. This analysis is particularly effective for identifying large-scale genetic defects.12