Gamete Formation in Animals

SpermatogenesisOogenesis

• Both Spermatogenesis and Oogenesis involve the process of meiosis, but they take place in different ways

Spermatogenesis

• The process of creating sperm.

• Takes place in the Testes of most animals.

• The process begins with a diploid (2n) cell called a Spermatogonium.

• At the beginning of puberty, the Spermatogonia reproduce through Mitosis.

Spermatogenesis

Spermatogenesis

• These diploid cells then undergo Meiosis to form 4 Haploid (n) cells.

• After Meiosis II, the new haploid cells undergo a final set of developmental stages.

• Afterwards, the cells are mature Sperm.

Oogenesis• The process of creating egg cells

• Takes place in the ovaries of most animals

• The process begins with a diploid (2n) cell called an oogonium.

• Oogonia reproduce by mitosis before birth and begin meiosis, but stop at Prophase I.

Oogenesis

• There is an uneven distribution of cytoplasm after meiosis I.

• The cell with most of the cytoplasm continues through meiosis I and II to form an egg.

• The other products are called polar bodies and degenerate.

• Meiosis II is not completed unless the egg is fertilized by a sperm cell.

Multiple Births

Errors During Meiosis

Cri du Chat

Klinefelters

Down’s Syndrome

Turner Syndrome