What is the process by which gametes (sex cells) are formed?

 The process by which gametes (sex cells) are formed is called meiosis. Meiosis is a type of cell division that reduces the number of chromosomes in half and produces four haploid cells. Meiosis consists of two stages: meiosis I and meiosis II. In meiosis I, homologous chromosomes pair up and exchange segments of DNA in a process called crossing over. Then, the homologous pairs separate and move to opposite poles of the cell. In meiosis II, the sister chromatids of each chromosome separate and move to opposite poles of the cell. The result is four genetically unique haploid cells that can fuse with another gamete during fertilization.