An otherwise diploid strain of yeast is trisomic for one chromosome. The strain carries a recessive allele a in one copy of the trisomic chromosome and the dominant allele A in each of the other copies, yielding the genotype AAa. Assume that the locus is tightly linked to the centromere and that the trisomic chromosome forms a bivalent and a univalent (monovalent) at random.

Explain why (or how) you would get tetrads that were either 4:0 ratio of dominant to recessive phenotype or 2:2.