User:Mary Tobias

Gametogenesis is the process by which gametes example the egg and sperm form.There are two types of gametogenesis in animals;

1.spermatogenesis in male, which is the process by which sperms form.spermatogenesis has two phase s.a) spermatocytogenesis; this phase is characterized by cell division that results in the formation of spermatids. b) spermiogenesis;this phase is characterized by maturation and differentiation of spermatids.

Stages of spermatocytogenesis; Spermatogonium: The process begins with spermatogonial stem cells located at the basal layer of the seminiferous tubules in the testes. These cells undergo mitotic divisions to maintain their population and produce two types of daughter cells.

Type A Spermatogonia: Some of the daughter cells remain as type A spermatogonia, which continue to divide mitotically, ensuring a constant supply of stem cells for future generations.

Type B Spermatogonia: Other daughter cells differentiate into type B spermatogonia. These cells are destined to undergo further development into primary spermatocytes.

Primary Spermatocyte (Spermatocyte Order I): Type B spermatogonia undergo another round of mitotic division, resulting in primary spermatocytes. Each primary spermatocyte is diploid (2n), containing a full set of chromosomes.

Meiosis I: Primary spermatocytes then enter meiosis I, where they undergo DNA replication and recombination during prophase I, which consists of five sub-stages: leptotene, zygotene, pachytene, diplotene, and diakinesis. This stage is crucial for genetic diversity as it allows for the exchange of genetic material between homologous chromosomes.

Secondary Spermatocyte (Spermatocyte Order II): After completing meiosis I, each primary spermatocyte divides into two secondary spermatocytes through a process called reduction division. Each secondary spermatocyte is haploid (n), containing half the number of chromosomes compared to the original cell.

Meiosis II: Secondary spermatocytes quickly proceed to meiosis II without further DNA replication, resulting in two haploid spermatids from each secondary spermatocyte

Stages of spermiogenesis; 1. Golgi stage; enzymes produced by Golgi bodies catalyze the formation acrosome. 2.Acrosomal stage; hardening of acrosome around the sperm nucleus. 3. Tail phase; is the elongation of centrioles to form the tail of sperm. 4. Maturation stage; spermatids loses some of its cytoplasm.

2. Oogenesis Is another type of gametogenesis which is the formation of egg cell or ovum. Phases of oogenesis a) Maturation before birth b) Maturation at puberty

a) Maturation before birth; The primordial germ cell differentiates to form oogonium. Oogonium undergoes multiple mitotic division and are arranged in clusters sorrounded by follicular cells. Further division of oogonium give up primary oocyte. b) Maturation at puberty; the oocyte continue to die until the number reaches 500. Each month 15 to 20 oocytes start the process of maturation however only one oocyte is ovulated.