Germ cell

Germ cell: A germ cell is a gamete (a sperm, an egg, or a cell that can become either). Germ cells are haploid cells, having a single set of 23 chromosomes containing half the usual amount of DNA and half the usual number of genes. All other body cells are somatic cells.

Male and female germ cells

Germ cells are significantly different in men and women. In men, germ cells (sperm cells) have tail-like outgrowths (flagella) and are relatively mobile. Female reproductive cells (ovules) are non-mobile and are larger than male gametes.

When male and female germ cells fuse together, the process is called fertilization. As a result, a zygote is born; this diploid cell contains a mix of inherited genes from both the father and mother.

The production of germ cells

Primary germ cells form in the fifth week of embryonic development in the yolk sac. Human germ cells are produced by gonads, which are organs of the reproductive system. They produce sex hormones necessary to grow and develop primary and secondary reproductive organs and structures.

The production of human germ cells is called meiosis. This is a two-step process of cell division, when replicated genetic material in the parent cell is distributed between the four daughter cells.

In egg development or oogenesis, daughter cells divide unevenly in meiosis. It leads to the formation of an oocyte (one large egg) and several polar bodies (smaller haploid cells), which do not have the ability to be fertilized and degrade later. 

Sperm production, or spermatogenesis, continuously occurs inside the male testicles.