The meiotic cell division comprises two successive nuclear division the meiosis I and meiosis II. The meiosis I have four stages prophase I, metaphase 1, anaphase 1, and telophase 1. The prophase I have further been divided into five phases depending on the chromosomal behavior.

The pachytene is the third phase of the five phases where the four chromatids appear as tetrads. Crossing over between two homologous chromosomes takes place during this phase and therefore leads to the recombination of the genetic material on the two chromosomes. In this phase the exchange of genetic material between sister chromatids of non- homologous chromosomes takes place. The variations in sexually reproducing organisms are the result of this genetic recombination.