1. Chromosomes are specific forms of DNA that exist in cells during mitosis or meiosis.
2. In the nucleus, DNA is tightly wrapped around proteins called histones and packaged into a linear structure.
3. When a cell does not divide, the chromosomes are invisible in the nucleus - even under a microscope.
4. However, the DNA that makes up chromosomes becomes more compact during cell division and can be seen under a microscope.
5. Each chromosome has a contraction point called centromere (dot), which divides the chromosome into two parts, namely "arm".
6. The short arm is "p arm"; The long arm is "q arm".
7. The position of the centromere (dot) on each chromosome provides a unique shape for the chromosome, which can be used to help describe the position of a specific gene.
8. Chromosomes are species-specific, and their number, size and shape vary with biological species, cell types and development stages.
