Why are cells arrested with colchicine during meta phase when creating a karyotype

Because they are organized in the "X " shape. When cells are dividing, you cant see the genetic materials.

Explanation:

Karyotypes are those that have a complete set of diploid chromosomes. It is a a chromosomal map. Karyotypes gets arrested during the meta phase or in the prometaphase. these are the stages of cell cycle. This happens during the condensation of the chromosomes.

During the time of mitosis, the condensation of chromosomes occurs and they will be formed as a separate individual and a visible thing. These freeze by colchicine during the stage of metaphase. This is because the organisation is in the shape of"X" and we can not visualize the genetic materials during cell division.