2 species

Metaphase of the first meiotic division: Homologous chromosomes are arranged in pairs on the equatorial plate. The second meiotic division process: ②Metaphase: The chromosomes are fixed in shape, clear in number, and freely arranged.

Chromosome is the specific form of DNA that exists in cells during mitosis or meiosis. Within the cell nucleus, DNA is tightly coiled around proteins called histones and packaged into a thread-like structure. When cells are not dividing, chromosomes are not visible in the nucleus - even under a microscope. However, the DNA that makes up chromosomes becomes closer together during cell division, and the chromosomes become visible under a microscope. Each chromosome has a constriction called the centromere, which divides the chromosome into two parts, the "arms." The short arm is the "p arm"; the long arm is the "q arm". The position of the centromere (point) on each chromosome gives the chromosome its characteristic shape and can be used to help describe the location of specific genes. Chromosomes are species-specific, and their number, size, and shape vary with biological species, cell types, and developmental stages.