Meiosis

• Gametes


  Sex cells with exactly half as many chromosomes as the starting cell
• Meiosis


  In humans, the process which takes us from a diploid mother cell to a haploid daughter cell with a single set of chromosomes
• Homologous chromosomes


  Similar but non identical pair that a person receives one of from each parent
• Meiosis I


  When homologous pairs separate in meiosis
• Meiosis II


  When sister chromatids separate in meiosis
• Prophase I


  Meiosis phase where chromosomes condense, but also pair up, unlike in mitosis, where they cross over to create two new remixed chromosomes
• Crossing over


  When the DNA on homologous chromosomes is broken at the same spot on both, then the different alleles of the same gene are switched. Process by which homologous chromosomes trade parts
• Synaptonemal complex


  Protein structure that holds chromosomes together during crossing over. Keeps them almost directly on top of each other so swapping is easy
• Chiasmata


  Cross shaped structure where homologues are linked together
• A homologous pair can cross over up to 25 times in prophase I
• Metaphase I


  When homologous pairs (not individual chromosomes) line up at the metaphase plate for separation. Which pairs end up getting put where is random, so you get randomly assigned gametes
• Anaphase I


  Meiosis phase where the homologues are pulled apart to opposite poles of the cell but sister chromatids stay together
• Telophase I


  Meiosis, chromosomes arrive at opposite poles of the cell, sometimes with the nucleus reforming and uncondensing DNA, but gets skipped a lot because the cell will just redivide anyways
• Meiosis II


  Mitosis but for haploid cells, where the chromatids being pulled apart are remixes so not completely identical
• Prophase II


  Meiosis: chromosomes condense if they haven't already, centrosomes pull apart, spindles start getting formed
• Metaphase II


  Meiosis: remixed sister chromatids are lined along the plate, captured my microtubules of spindles from opposite poles
• Anaphase II


  Meiosis: remixed sister chromatids are pulled apart and brought towards opposite poles of the cell
• Telophase II


  Nuclear membranes form around all sets of remixed chromosomes, which decondense. Cytokinesis splits them up, and you end up with four gametes