Meiosis Gamete Production 1 Meiosis Different from Mitosis

Meiosis Gamete Production 1

Meiosis Different from Mitosis because: Involves 2 cell divisions Results in 4 cells with 1/2 the normal genetic information. 2

Meiosis Vocabulary: Diploid (2 N) - Normal amount of chromosomes Haploid (N) - 1/2 the chromosomes Meiosis results in the formation of haploid cells. 3

Meiosis I Prior to division (S phase), amount of DNA doubles 4

Metaphase I: Homologous (same) chromosomes line-up along the metaphase plate or equator Genes are exchanged at connections called Chiasmata. 5

Crossing Over Segments of chromosomes break and reattach at similar locations. Results in new genetic combinations. The main advantage of sexual reproduction 6

Chiasmata 7

Anaphase I: Each Chromosome is pulled to opposite sides of the cell. Cytokinesis: May or may not occur. 8

Meiosis II DNA DOES NOT double Metaphase II: Chromosomes randomly line-up along metaphase plate like regular mitosis. Anaphase II: Sister chromatids are pulled to opposite sides of the cell. Telophase II: Nuclei reform and cytokinesis usually occurs (although it is often unequal). Sister chromatids 9

Meiosis Gametes: Ova (egg) and sperm. Ova: Produced in the ovaries in females Process is called oogenesis Sperm: Produced in the testes of males. Process is called spermatogenesis 10

Spermatogenesis & Oogenesis Sperm formation Egg formation 11

Overview of Meiosis 12