Meiosis

• Prophase 1/Crossing Over

  • when chromosomes condense during prophase 1 the homologous pair physically connect to each other
  • synapsis is forming structures called tetrads
  • at each connection chiasma, DNA is exchanged between the homologous pairs
  • Every chromatid that Is produced has a unique combination of DNA from both chromosomes in a pair
  • the homologous chromosomes are first helped by a protein structure called the synaptonemal complex (before the chiasma because it breaks down)
  • multiple crossover can occur (up to 25)
• Synapsis 


  the process in which the 2 homologous chromosomes line up to come together to create the chiasma
• Chiasma 


  the structure formed between a pair of homologous chromosomes where link or connect to crossover
• Tetrads

  synapsis forma tetrads - two homologous chromosome, with a total of four sister chromatids held together by the chiasma
• Metaphase 1

  • homologous pairs of chromosomes line up at the metaphase plate still attached to each other
  • the orientation of each pair is random
  • how they arrange themselves among the metaphase plate creates variation
• Anaphase

  the homolugues are pulled apart and move apart to opposite ends of the cell and sister chromatids remained attached
• Telophase

  • Chromosomes arrive at opposite poles of the cell
  • nuclear membrane reforms, chromosomes decondense
• Meiosis 2

  Prophase: chromosome condense, nuclear envelope breaks down, spindle microtubules began to capture chromosomes

  Metaphase: chromosomes line up individually along metaphase plate

  Anaphase: sister chromatids seperate and are pulled towards opposite piles of the cell

  Telophase: nuclear membrane forms around chromosome, chromosomes decondense. Cytokinesis splits chromosomes sets forming 4 haploid cells