Here's why:
* Chromosomes condense: During cell division, specifically in the prophase stage of mitosis or meiosis, the chromosomes condense and become tightly coiled. This makes them much thicker and easier to see under a microscope.
* Chromosomes align: In the metaphase stage, the condensed chromosomes align along the equator of the cell, further increasing their visibility and making it easier to count them.
* Sister chromatids: During cell division, each chromosome is made up of two identical copies called sister chromatids. These sister chromatids are held together by a structure called the centromere, which is another distinctive feature visible during cell division.
In contrast, when cells are not dividing, their chromosomes are in a less condensed, unwound state. This makes them difficult to see and count under a microscope.
Therefore, studying dividing cells allows biologists to clearly visualize and count the chromosomes, determining the organism's chromosome number, which is a key characteristic of a species.
