Meiosis: Creation of the Sex Cells

What is Meiosis?? Meiosis- creation of sex cells (eggs, sperm) Meiosis- creation of sex cells (eggs, sperm) Occurs in testes in males, ovaries in females Occurs in testes in males, ovaries in females At the end, 4 cells are created that are NOT identical to the starting cell. At the end, 4 cells are created that are NOT identical to the starting cell.

Karyotypes Display of the 46 chromosomes of an individual Display of the 46 chromosomes of an individual 23 homologous pairs of chromosomes 23 homologous pairs of chromosomes Female Male

Homologous Chromosomes Two chromosomes of each matching pair Two chromosomes of each matching pair –1 from mom & 1 from dad

Diploid/ Haploid Diploid (2n)- cells with 2 homologous sets of chromosomes (2n= 46 in humans) Diploid (2n)- cells with 2 homologous sets of chromosomes (2n= 46 in humans) Haploid (n)- Single set of chromosomes (n= 23 in humans) Haploid (n)- Single set of chromosomes (n= 23 in humans) –Sex cells produced through meiosis

Human Life Cycle

Mitosis vs. Meiosis MITOSISMEIOSIS MITOSISMEIOSIS –Body cells - Gametes –Produces 2 identical- Produces 4 different cells (diploid) cells (haploid)

Meiosis 2 parts- Meiosis I and Meiosis II 2 parts- Meiosis I and Meiosis II

Video Meiosis Meiosis Meiosis

Crossing Over Human offspring are genetically different from their parents… Human offspring are genetically different from their parents… WHY?? WHY?? Occurs during Prophase I Occurs during Prophase I Homologous chromosomes exchange some genetic material Homologous chromosomes exchange some genetic material Why is this important?? Why is this important?? –Allows for more variation in the cells.

Crossing Over

Mitosis vs. Meiosis

Describe two differences between meiosis and mitosis. Describe two differences between meiosis and mitosis. –1) –2) Video Video Video