Meiosis and Sexual Reproduction

Meiosis Reduction/Division Begins after Interphase, when ______ replicates. DNA Reduction: Process takes a ______ cell with two sets of chromosomes and reduces it to a _________ cell with one set of chromosomes Division The cytoplasmic division of one cell into _____ cells. diploid four haploid

Meiosis: Reduction/Division Two divisions: Meiosis I & Meiosis II

Prophase I Unlike Mitosis: Like Mitosis: Homologous chromosomes group with other homologous chromosomes to form a “tetrad” A “chiasma” occurs at the point where the chromosomes cross over, detach, and exchange segments of the chromosome Like Mitosis: Nuclear membrane disappears Spindles form Chromatin condenses into chromatids

Metaphase I Homologous chromosomes line up at the metaphase plate. Microtubules (spindles) attach to the kinetochore of centromere

Anaphase I Homologous chromosomes separate. Sister chromatids remain attached.

Telophase I Two daughter cells are formed with each one containing only one chromosome of the homologous pair. The daughter cells are now haploid.

Meiosis II: Gamete formation Prophase II: DNA does not replicate. Prophase II is just like mitotic prophase.

Metaphase II: All of the chromosomes line up at the metaphase plate.

Anaphase II: Centromeres divide Sister chromatids migrate separately to each pole.

Telophase II / Cytokinesis: Chromosomes revert to chromatin. Nuclei reform. Cytoplasm cleaves Four haploid daughter cells are obtained

Summary of Meiosis (video)

What is the difference between mitosis and meiosis? (flash) Based on the image alone, fill in the Venn Diagram comparing and contrasting mitosis from meiosis. Then watch the flash video with your class, and add information to your graphic organizer.