Meiosis and Genetic Variation

• What are the two types of cell division in eukaryotic organisms?

  Mitosis and Meiosis
• What is mitosis?

  Cell division, 2 genetically identical diploid daughter cells
• What is meiosis?

  cell division that makes four genetically dissimilar haploid gametes.
• In ferns what is the difference in divisions with gametes being produced compared to spores being produced?

  gametes - mitosis

  spores-meiosis
• As well as producing haploid cells, meiosis produces what?

  Cells with genetic variation
• What are the two ways meiosis creates variation within genes?

  independent assortment

  crossing over of homologous pairs
• Define bivalent.

  The association of two replicated homologous chromosomes having exchanged DNA strands in at least one site called chiasmata.
• What is the chiasmata?

  Crossing over of genetic material during meiosis.
• What is independent assortment?

  when the homologous pairs line up at the spindle, we cannot predict which gamete will end up with the maternal or paternal chromosome.
• What is crossing over/recombination?

  chromatids become twisted around one another causing portions of the chromatids to break off and exchange places on the homologous pair.
• What happens during Prophase 1?

  1. chromosomes condense

  2. homologus pairs form chiasmata

  3.nuclear membrane breaks down

  4.spindle fibres start to form
• What happens during metaphase 1?

  1. pairs of homologous chromosomes line up along the equator randomly
• What happens during anaphase 1?

  spindle fibers shorten and homologous pairs get pulled to opposite poles of the cell.
• What happens during telophase 1?


  carry on from here