Spermatogenesis The creation of sperm cells using mitosis, meiosis, and differentiation

Spermatogenesis Overview • • Germ cell Germ cells divide by mitosis Meiosis review Germ cell 2n Mitosis Overview 1° spermato cytes 2n • Germ cells divide by mitosis Diploid 1° spermatocytes divide by the first division of meiosis into haploid 2° spermatocytes These divide by meiosis II into haploid spermatids The spermatids mature into sperm cells (spermatozoa) by the process of differentiation – nursed by Sertoli cells. Meiosis I 2° spermato cytes n 2° spermato cytes n • Meiosis II Spermatid n Spermatid n Spermatid n Spermatid n Sperm cell Sperm cell Sperm cell Sperm cell

Cross section showing the different stages

Oogenesis The creation of female gametes - using mitosis, meiosis, and differentiation

Oogenesis Germ cells (oogonia) in the ovary divide by mitosis. Outline Germ cells (oogonia) in the ovary divide by mitosis. 1° oocytes produced begin meiosis I – in a structure called the 1° follicle. Meiosis I is completed before ovulation and a 2° oocyte is formed (in a 2° follicle) – the polar body usually degenerates. Only after fertilisation will meiosis II be completed and a mature ovum formed by differentiation. The second polar body will degenerate

Stages of Oogenesis