Beth Walker CP Biology

 failure of homologous chromosomes to separate correctly during anaphase I or II of meiosis.

 Makes gametes with one extra OR one less chromosome

 Monosomy  has 1 less chromosome Ex. sperm (22) + egg (23) = baby (45)

 Trisomy  has 1 extra chromosome Ex. sperm (23) + egg (24) = baby (47)

 Turner’s Syndrome  45 chromosomes *Mother only gives 22 chromosomes *Father gives 23 chromosomes

 Down’s Syndrome  extra chromosome #21

 Klinefelter’s Syndrome  extra sex chromosome (#23)

 When none of the homologous chromosomes separate  the gamete stays diploid(2n) instead of separating and becoming haploid(n)  Ex. 2n gamete + n gamete = 3n baby (triploid) (abnormal) (normal) 2n gamete + 2n gamete = 4n baby (tetraploid)

 Extra sets of chromosomes  polyploidy  Polyploidy is common in plants, but rare in animals (usually leads to death of the zygote in animals)