Independent Assortment
In meiosis I, the lining up of paternal and maternal homologues
is random (or independent of what the other chromosome in
the pair is doing).
For a cell with 2 pairs of chromosomes (2n = 4): 4 possible
combinations of chromosomes in gametes.
Combinations = 22 = 4 (formula is 2x where x = # of pairs)
For a cell with 3 pairs of
chromosomes (2n = 6): 8
possible combinations of
chromosomes in gametes.
Combinations = 23 = 8
For a cell with 4 pairs of
chromosomes (2n = 8):
16 possible combinations
of chromosomes in
gametes.
Combinations = 24 = 16
Independent assortment of homologues in humans produces
223 (8,388,608) different combinations of chromosomes. Wow!
The consequence of this is that no two gametes are likely to
have the same genetic complement. This results in genetically
varied offspring, though NO NEW genetic information has been
made.
Coupled with crossing over and segregation of alleles the
likelihood of offspring from the same two parents being
genetically the same is miniscule.