eli5 what gametogenesis is
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Gamete = sperm or egg
Genesis = creation of
Gametogenesis = process of making sperm cells (in XY people) or oocytes/eggs (in XX people).
Happens in the testes or in the ovaries. These gametes have 23 chromosomes each, and when sperm+egg meet to make a baby, the baby will have normal 46 chromosomes.
Simply put: it’s the making of your gametes. What are gametes, these are either egg or sperm cells depending on ones biological sex. Gametogenesis usually comes about because of meiosis. Gametogenesis for making sperms is called spermatogenesis, that for making egg cells is known as oogenenis.
Spermatogenesis:
You have a spermagonium in the seminiferous tubules in the testicle that goes through mitosis to become a primary spermatocyte. This primary spermatocyte will go through meoisis I to become a secondary two spermatocytes, which have their genetic material halved. Secondary spermatocytes goes through meiosis 2 and become 4 spermatids. These spermatids mature and differentiate to become sperm cells with a tail.
Oogenesis:
This one is a little more complicated but occurs in three phases. These phases are multiplication, growth and maturation.
Multiplication happens in the ovaries of unborn babies. This phase involves the germinal epithelial cells in the ovaries undergoing mitosis to become oogonia.
Each oogonium enters the growth phase in puberty, when the person starts their monthly periods. In this phase, each oogonium grows very big, and is now called the primary oocyte. The primary oocyte undergoes meiosis I and splits into two: a secondary oocyte and a smaller polar body.
In the maturation phase, they both undergo meiosis 2, however, the polar body splits into 3 degenerate cells, meaning they cannot be used. But, the secondary oocyte becomes a mature ovum.
As with most scientific terms, it’s helpful to break it up into its Latin or Greek (in this case, Greek) origins. In this case, it’s *gamete* (a type of cell, but ultimately from the Greek word for “husband” or “wife”) + *genesis* (“creation” or “start”, literally “birth”). So it’s the “creation” (*genesis*) of “gametes” (*gameto-*). If you know what gametes are, that already gives you some tools to guess the meaning.
But that aside: *gametes* are the cells that are involved in sexual reproduction. In humans, the gametes are sperm cells (produced by men*) and egg cells (by women). During sexual reproduction (in the case of humans, during sex that produces a child), sperm cells are brought into contact with egg cells; the sperm cell merges with the egg cell and releases the father’s half of the child’s genetics into the egg cell. That half combines with the mother’s half of the child’s genetics, already present in the egg, to form the genes of the child.
*Gametogenesis*, then, is how you make those cells. Specifically, it’s the process by which the cells of the mother and father split in ways that produce egg and sperm cells. The most important piece of this process is [*meiosis*](https://en.wikipedia.org/wiki/Meiosis) (pronounced “my-oh-sis”), a form of cell division that is different from the *mitosis* that is normally how cells reproduce. In mitosis, a cell produces two identical daughter cells; in meiosis, a cell produces *four* non-identical daughters that each carry half of the original’s DNA.
(* Setting aside trans or intersex people for a moment, since we’re talking about normal reproduction here.)
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