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Inheritance - Coggle Diagram

- - - - Carry the same genes in the same positions (locus)
        Are the same shape
- - - - DNA condenses and becomes visible as chromosomes
      - DNA replication has already occurred so each chromosome consists of two sister chromatids joined together by a centromere
      - The chromosomes are arranged side by side in homologous pairs
      - A pair of homologous chromosomes is called a bivalent
      - As the homologous chromosomes are very close together the crossing over of non-sister chromatids may occur. The point at which the crossing over occurs is called the chiasma (chiasmata; plural)
      - In this stage centrioles migrate to opposite poles and the spindle is formed
      - The nuclear envelope breaks down and the nucleolus disintegrates
    - - The chromosomes arrive at opposite poles
      - Spindle fibres start to break down
      - Nuclear envelopes form around the two groups of chromosomes and nucleoli reform
      - Some plant cells go straight into meiosis II without reformation of the nucleus in telophase I
    - - Cytokinesis
      - This is when the division of the cytoplasm occurs
      - Cell organelles also get distributed between the two developing cells
      - In animal cells:
      - The cell surface membrane pinches inwards creating a cleavage furrow in the middle of the cell which contracts, dividing the cytoplasm in half
      - In plant cells:
      - Vesicles from the Golgi apparatus gather along the equator of the spindle (the cell plate). The vesicles merge with each other to form the new cell surface membrane. Layers of cellulose are laid down to form the primary and secondary walls of the cell
      - The end product of cytokinesis in meiosis I: two haploid cells
      - These cells are haploid as they contain half the number of centromeres