In a cross in Drosophila, a female heterozygous for the autosomally linked genes a, b, c, d, and e (abcde/+++++) was testcrossed with a male homozygous for all recessive alleles. Even though the distance between each of the loci was at least 3 map units, only four phenotypes were recovered, yielding the following data:

Phenotype Frequency

+++++ 440

abcde 460

++++e 48

abcd+ 52

Why are many expected crossover phenotypes missing? Can any of these be mapped from the data given here? If so, determine the map distances.