qs

• explain the importance of meiosis in formation of human sperm and egg cells

  • meiosis allows genetic variation in gametes
  • through independent assortment
  • through crossing over
  • meiosis halves the chromosome number
  • so that fertilisation of chromosomes is restored
• explain why the DNA in the 2 sister chromatids is identical

  • DNA helicase breaks hydrogen bonds between 2 DNA strands/ unzips DNA
  • each DNA strand acts as a template/ both strand copied
  • complementary base pairing rule with free DNA nucleotides
  • sugar phosphate backbone forms