In prenatal cases, amniotic fluid or chorionic villus sampling (CVS) is used to extract fetal cells. This culturing period, which typically lasts 72 to 96 hours, is critical because chromosomes are only visible to the naked eye when the cell is actively preparing to divide.
Karyotype Analysis Preparation Steps: From Cell Culture to Chromosome Staining
To achieve this arrest, a chemical agent called colchicine or colcemid is introduced to the culture. Timing is crucial in this step; if the cells are exposed to the arresting agent for too long, they may degrade, while too short an exposure results in poor chromosome spreading.
Following the hypotonic shock, the cells are fixed in a Carnoy's solution—a mixture of methanol and acetic acid. A trypsin enzyme briefly treats the chromosomes, followed by staining with Giemsa dye.
Karyotype Analysis Preparation Steps: From Cell Culture to Chromosome Staining
This fixative hardens the cells and removes excess moisture, ensuring that the chromosomes remain intact and tightly coiled during the next steps. The harvesting process involves gently separating the cells from the growth medium and treating them with a hypotonic solution.
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