Genetic Code & Cell Function

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  • Genetic Code & Cell Function
    • Meiosis 2
      • Prophase 2
        • New spindles begin to form at right angles to the spindles in prophase 1
      • Metaphase 2
        • Chromosomes arrange themselves on the equator of the spindle fibres
        • Each chromosome is attached to the spindle via the centromere
      • Anaphase 2
        • Centromeres divide
        • Spindle fibres contract
        • Chromatids are pulled to the opposite poles
      • Telophase
        • Chromatids uncoil and lengthen
        • Spindles disappear
        • Nuclear envelope reforms
        • 4 daughter haploid cells
    • Significance of Meiosis
      • Meiosis halves the chromosome numbers = haploid chromosomes
      • Genetic variation in the gametes and therefore in the zygote
      • Two main ways genetic variation occurs
        • Crossing over during prophase 1
        • Independent assortment during metaphase 1
      • Random fusion of gametes
        • Produces more variation in the offspring
    • Differences between meiosis 1 & meiosis 2
      • Crossing over occurs in Prophase 1 but not Prophase 2
      • Homologous bivalents align at the equator in Metaphase 1
        • Chromosomes align at the equator in Metaphase 2
      • Independent assortment occurs in Metaphase 1
        • It does not occur in Metaphase 2
      • 2 daughter cells are formed in meiosis 1
        • 4 daughter cells are produced in meiosis 2
        • All daughter cells are haploid

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