A kind of cell division, which leads to the formation of four daughter cells each comprising half of the number of the chromosome of the parent cell, as in the generation of plant spores and gametes is known as meiosis.
In meiosis, when cross over takes place between the chromatids, the homologous chromosomes trade the segments of genetic substance, leading to the formation of a new combination of alleles. The phenomenon of crossing over takes place at the time of prophase I of meiosis prior to the alignment of the tetrads along the equator in the metaphase I stage.
It is Metaphase 1. It's Metaphase 1 because in the pachytene stage, the chromosomes appear as independent. They are also adjusted (homologous chromosomes).
