Cells from the fluid are cultured and a karyotype test – an analysis of the cells' chromosomal makeup – is performed.

Karyotyping is a powerful tool used in genetics to evaluate the chromosomal composition of an organism. In this process, cells are cultured to promote the growth of cell division. Once enough cells are obtained, a karyotype analysis is conducted by stopping the cell cycle at metaphase, where chromosomes are most visible.

1. Isolation of Cells: Fluid samples, which may contain relevant cells (such as amniotic fluid or blood), are collected and cells are isolated for culture.
2. Cell Culture: The isolated cells are placed in a growth medium that allows them to multiply. This step is crucial as a sufficient number of cells are needed for analysis.
3. Cell Division Arrest: After sufficient growth, the division of cells is halted using a drug that disrupts the spindle apparatus (commonly Colcemid).
4. Chromosome Preparation: Cells are then lysed, typically using a hypotonic solution that causes them to swell, which helps in spreading out the chromosomes for easier observation.
5. Staining: Chromosomes are stained using specific dyes that provide a distinct banding pattern, making it easier to identify the chromosomes during analysis.
6. Microscopy: The stained chromosomes are observed under a microscope, typically using digital imaging to capture their morphology.
7. Analysis: The final step involves arranging the chromosomes in pairs by size and shape, which allows for the identification of any chromosomal abnormalities such as aneuploidy or structural changes.

Karyotype tests can be critical in diagnosing genetic disorders, identifying chromosomal abnormalities that may lead to conditions such as Down syndrome, Turner syndrome, or various cancers. It provides essential information about the genetic health of the individual being analyzed.