Sexual Reproduction and Meiosis Chapter 11

Insert Good Title Here…. Gametes Somatic Cells Germ Line Cells Zygote What does Meiosis do and Why is it important?

Sexual Life Cycles Algae and Fungi Most Animals Some plants and some algae Figure 11.2

What Makes Meiosis Different from Mitosis? Synapsis Crossing over and Recombination Separation during Anaphase 1 2 divisions with only 1 replication stage

Parts of Meiosis Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Prophase II Metaphase II Anaphase II Telophase II

Prophase I DNA condenses and Chromosomes become visible Synapsis Occurs Crossing Over Occurs Chiasmata

Metaphase 1 Homologous Chromosomes line up on Metaphase Plate Microtubules attach to kinetochores of each homologue (but not individual chromatids)

Anaphase 1 Homologues are pulled apart…what about chromatids? Independent Assortment

Telophase 1 Cells Complete Separation and nuclear envelope reforms Cytokinesis may or may not occur

Prophase II Nuclear Envelope Breaks Down New Spindle Forms

Metaphase II Chromosomes Line up along Metaphase Plate Microtubules attach to each sister chromatid

Anaphase II Sister Chromatids are pulled apart

Telophase II Nuclear Envelope Reforms Cytokinesis Follows

Problems with Meiosis Nondisjunction Aneuploid Gametes

Key Points of Meiosis 1. Pairing of homologues and crossing over that joins maternal and paternal homologues 2. Co-segregation of sister centromeres during anaphaseI due to maintenance of sister chromatid cohesion as sister centromeres 3. The attachment of sister kinetochores to the same pole in meiosis I and to opposite poles in mitosis 4. Suppression of replication between two meiotic divisions