Describe game formation. Mension process of spermatogenesis and oogenesis

During life cycle of most animals some diploid cells undergo meiosis and haploid gametes form in a process called gametogenesis. The testes of the male, produces sperms and is called spermatogenesis, in the ovaries of female, the production of oval (eggs) is called oogenesis.

Spermatogenesis:

Spermatogenesis produces mature sperm as follows:

(1)        Spermatogenesis begins in unspecialized germ cells called spermatogomia (singular spermatogonium). The spermatogonium enlarges and becomes primary spermatocyte.

(2)        A primary spermatocyte undergoes meiosis (meiotic division I) and produces two smaller secondary spermatocytes).

(3)        Both secondary spermatocytes undergo second meiotic division (meiotic division II) to form spermatids each primary spermatocyte gives rise to four spermatids, each with the haploid number of chromosomes.

(4)        Spermatids develop into mature sperm (spermatozoa) without undergo going any further cell division.
Oogenesis:

Oogenesis, the maturation of ova (singular, ovum) or eggs differ from spermatogenesis in several ways and proceeds as follows:

(1)        Oogenesis begins in unspecialized germ cells called oogonia which undergo mitosis.

(2)        An oogonium develops and grows into primary oocyte which contains diploid number of chromosomes. The primary oocyte undergoes first meiotic division to produce two daughter cells of unequal size.

(3)        Larger of the daughter cells in the secondary oocyte, which contains almost all of the primary occytes, food rich cytoplasm which provides nourishment for the developing ovum.

(4)        Smaller of the two daughter cells is first polar body and is essentially only a nucleus. It may divide again but eventually it degenerates.

(5)        In some animals, if the secondary oocyte is fertilized, it begins second meiotic division, producing haploid ovum and another tiny polar body forms. This second polar body is also destined to disintegrate. With the haploid sperm now ovum nuclei merge (syngamy), the ovum becomes a zygote. Notice that in oogenesis each primary oocyte gives rise to only one functional gamete instead of four as in spermatogenesis.


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