Meiosis

thumb|300x300px|In meiosis, the chromosomes duplicate (during [[interphase) and homologous chromosomes exchange genetic information (chromosomal crossover) during the first division, called meiosis I. The daughter cells divide again in meiosis II, splitting up sister chromatids to form haploid gametes. Two gametes fuse during fertilization, forming a diploid cell (zygote) with a complete set of paired chromosomes.]]

Oogenesis () or ovogenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. Oogenesis is initiated during embryonic development.

thumb|Normal spermatogenesis, testis biopsy. thumb|High-power view of a seminiferous tubule with normal spermatogenesis. Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testicle. This process starts with the mitotic division of the stem cells located close to the basement membrane of the tubules. These cells are called spermatogonial stem cells. The mitotic division of these produces two types of cells. Type A cells replenish the stem cells, and type B cells differentiate into primary spermatocytes. The primary spermatocyte

thumb|upright=1.35|Diagram of cytokinesis

300px|thumb|Image of kinetochores in pink

The pachytene stage (/ˈpækɪtiːn/ PAK-i-teen; from Greek words meaning "thick threads".), also known as pachynema, is the third stage of prophase I during meiosis, the specialized cell division that reduces chromosome number by half to produce haploid gametes. It follows the zygotene stage and is followed by the stage diplotene.

Zygotene (from Greek for "paired threads") is the second stage of prophase I during meiosis, the specialized cell division that reduces the chromosome number by half to produce haploid gametes. It follows the Leptotene stage and is followed by Pachytene stage.

cell cycle phase which is the first stage of prophase I in meiosis, and during which the chromosomes first become visible

protein family