Metaphase 1

• how do the chromosomes arrange themselves in metaphase 1?

  pairs of homologous chromosomes arrange themselves at the equator of the spindle
• where are the chromosomes from in a homologous pair?

  one chromosomes is from the father and one chromosome is from the mother
• what is the assortment of the chromosomes when they lie at the equator?

  • they lie at the equator randomly, with either one facing either pole
  • so a combination of paternal and maternal chromosomes faces each pole and the combination of chromosomes that goes into each daughter cell at meiosis 1 is random with respect to which parent they came from
  • this is called independent assortment of chromosomes
• what is independent assortment?

  • either of a pair of homologous chromosomes faces to either pole at metaphase 1 of meiosis, independently of the chromosomes of other homologous pairs
  • either of a pair of chromatids faces to either pole at metaphase 2, independently of the chromatids of other chromosomes
• what does independent assortment of chromosomes produce?

  it produces new genetic combinations, with genes from both parents going into both daughter cells
• how many possible combinations of maternal and paternal chromosomes in the gametes are there when independent assortment happens with 3 pairs of chromosomes?

  2$^3$= 8
• how many possible combinations of maternal and paternal chromosomes in the gametes are there when independent assortment happens with 23 pairs of chromosomes?

  2$^{23}$= 8,388,608
• how many possible combinations of maternal and paternal chromosomes in the gametes are there when independent assortment happens with 2 pairs of chromosomes?

  2$^2$= 4
• what would happen to the number of different ways genes from the 2 parents could assort into gametes if there was no genetic crossing over?

  nothing, there would still be a very large number of different ways
• what is this an image of?

  independent assortment of 2 homologous pairs