Final answer:
Biologists create a karyotype by stimulating cells to divide, arresting them in metaphase, swelling them with a hypotonic solution, then staining and arranging the chromosomes into a karyogram to identify chromosomal abnormalities.
Step-by-step explanation:
How Biologists Create a Karyotype
Biologists make a karyotype to identify chromosomal abnormalities by collecting cells, such as white blood cells, from a blood sample or other tissue. In the laboratory, these cells are stimulated to divide actively, and a chemical like colchicine is applied to arrest condensed chromosomes during the metaphase stage of cell division. The cells are then treated with a hypotonic solution, causing them to swell and the chromosomes to spread out. Next, the sample is fixed with a preservative and applied to a microscope slide.
The geneticist proceeds to stain the chromosomes using a dye like Giemsa, which reveals the distinct banding patterns of each chromosome pair when viewed under bright-field microscopy. The banding patterns, size, and centromere locations of the chromosomes are used to identify them. Finally, the geneticist captures a digital image of the stained chromosomes and manually arranges them in numerical order to complete the karyotype. This results in a visual representation, called a karyogram or ideogram, of the individual's full set of chromosomes.