Meiosis and genetic variation

• Fertilisation


  haploid sperm fuses with haploid egg cell making a cell with normal diploid number if chromosomes, half from mother, half from father.

  Mixing of genetic material in sexual reproduction increases genetic diversity
• Meiosis process

  1. Before meiosis, DNA unravels and replicates so they're two copies of each chromosome called chromatids.
  2. DNA condenses forming double armed chromosomes by two sister chromatids attached by a centromere
  3. Meiosis I (first division) chromosomes are arranged in homogolous pairs
  4. homologous pairs separated halving chromosome number
  5. Meiosis II (2nd division) pair of sister chromatids making up each chromosome divided (centromere divided)
  6. 4 genetically different haploid cells produces
• Genetic variation in gametes: Crossing over chromatids

  • During meiosis I, homologous pairs pair up, chromatids twist around each other and parts of chromatids swap over, chromatids still contain same genes but different combination of alleles.
• Independent segregation

  • during meiosis I, homologous pair separated, its completely random which chromosome from each pair ends up in each daughter cell. Four daughter cells produced by meiosis cave different combinations of maternal and maternal chromosomes.
  • Shuffling of chromosomes = genetic variation