1. Important Terms
1.1. Chiasmata
1.2. Synapsis
1.2.1. "The tight pairing of the homologous chromosomes is called synapsis. In synapsis, the genes on the chromatids of the homologous chromosomes are aligned precisely with each other."
1.3. Tetrad
2. Purpose/Goal
2.1. Division of Gamete (Sperm andEgg) cells; forms haploid cells (cellsthat contain two copies from twohomologous chromosomes).
3. Difference Between Mitosis
3.1. Mitosis
3.1.1. Produces 2 daughter nuclei, in one division
3.2. Meiosis
3.2.1. Produces 4 daughter cells, in two divisions
3.3. Produces 4 daughter cells, in two divisions
4. Meiosis II
4.1. Prophase II
4.1.1. "Sister chromatids condense. A new spindle begins to form. The nuclear envelope starts to fragment."
4.2. Prometaphase II
4.2.1. "The nuclear envelope disappears, and the spindle fibers engage the individual kinetochores on the sister chromatids."
4.3. Metaphase II
4.3.1. "Sister chromatids line up at the metaphase plate."
4.4. Anaphase II
4.4.1. "Sister chromatids are pulled apart by the shortening of the kinetochore microtubules. Non-kinetochore microtubules lengthen the cell."
4.5. Telophase II and Cytokinesis
4.5.1. "Chromosomes arrive at the poles of the cell and decondense. Nuclear envelopes surround the f four nuclei. Cleavage furrows divide the cells into four haploid cells."
5. Meiosis I
5.1. Prophase I
5.1.1. Crossing Over
5.1.1.1. Crossing Over is the process in certain genes "found at particular spots on the chromosome" break and reconnect in a "criss-cross pattern so that the so homologues exchange part of their DNA."
5.1.2. Chromosomes condense and "pair up."
5.1.2.1. ("Each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length."- Khan Academy)
5.1.3. Chromosomes condense and "pair up."
5.2. Prometaphase I
5.2.1. Spindle fiber microtubles are attached to the kinetochore proteins at the centromeres.
5.2.1.1. "Kinetochore proteins are multiprotein complexes that bind the centromeres of a chromosome to the microtubules of the mitotic spindle." -OpenStax Biology
5.2.1.2. "Microtubules grow from centrosomes placed at opposite poles of the cell. The microtubules move toward the middle of the cell and attach to one of the two fused homologous chromosomes. The microtubules attach at each chromosomes' kinetochores. With each member of the homologous pair attached to opposite poles of the cell, in the next phase, the microtubules can pull the homologous pair apart. A spindle fiber that has attached to a kinetochore is called a kinetochore microtubule."
5.2.1.3. "At the end of prometaphase I, each tetrad is attached to microtubules from both poles, with one homologous chromosome facing each pole. The homologous chromosomes are stillheld together at chiasmata. In addition, the nuclear membrane has broken down entirely."
5.3. Metaphase I
5.3.1. The homologous chromosomes line up (orienting themselves, randomly--this affects genetic variation) at the "equator" of the cell "with the kinetochores facing opposite poles."
5.4. Anaphase I
5.4.1. "The microtubules pull the linked chromosomes apart. The sister chromatids remain tightly bound together at the centromere. The chiasmata are broken in anaphase I as the microtubules attached to the fused kinetochores pull the homologous chromosomes apart." -OpenStax Biology.
5.4.2. Image
5.5. Telophase I and Cytokinesis
5.5.1. the first meiotic division results in...
5.5.1.1. TWO HAPLOID CELLS