Final answer:
Crossovers are expected to occur in 100% of the tetrads when two linked genes are more than 50 map units apart, as they behave as if unlinked, exhibiting independent assortment.
Step-by-step explanation:
When two linked genes are more than 50 map units (Mu) apart, a crossover can be expected to occur between them in 100% of the tetrads. This is because a genetic distance of 50 map units corresponds to a recombination frequency of 50%, which is the maximum observed for linked genes. The notion of 50 Mu correlating with a 50% recombination frequency is based on the work of Alfred Sturtevant, who created genetic maps using centimorgans (cM) as units of measurement. If two genes are more than 50 cM apart, they behave as if they are unlinked; thus, crossovers happen as though the genes are on different chromosomes, resulting in a recombination frequency that mirrors independent assortment.