Gamete (sperm and egg) Production Meiosis Gamete (sperm and egg) Production

Meiosis Involves 2 cell divisions Results in 4 cells with 1/2 the normal genetic information. Start with 1 diploid end with 4 haploid Vocabulary: Diploid (2N) - Normal amount of genetic material Haploid (N) - 1/2 the genetic material.

Meiosis In Humans, these are the Egg and sperm. Meiosis results in the formation of haploid cells. In Humans, these are the Egg and sperm. Meiosis occurs in 2 phases: Meiosis I & Meiosis II

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

Metaphase I Metaphase I homologous chromosomes line-up along the metaphase plate or EQUATOR Mom and dad chromosomes = homologous chromosomes

Crossing Over Segments of homologous chromosomes break and reattach at similar locations. Results in new genetic combinations of offspring. This is the main advantage of sexual reproduction

Anaphase I During Anaphase I, each HOMOLOGOUS CHROMOSOME is pulled to opposite sides of the cell.

Meiosis II Chromosomes randomly line-up along metaphase plate like regular mitosis. Start with 2 haploid and end with 4 haploid Same steps as mitosis Sister chromatids

Overview of Meiosis

Non disjunction When sister chromatids or homologous chromosomes fail to separate

Trisomy 21 (Down Syndrome) Non disjunction on the 21st chromosome)