A Drosophila experiment examining potential genetic linkage of X-linked genes studies a recessive eye mutant (echinus), a recessive wing-vein mutation (crossveinless), and a recessive bristle mutation (scute). The wild-type phenotypes are dominant. Trihybrid wild-type females (all have the same genotype) are crossed to hemizygous males displaying the three recessive phenotypes. Among the 20,765 progeny produced from these crosses are the phenotypes and numbers listed in the table. Any phenotype not given is wild type. Phenotype Number 1. Echinus     8576 2. Scute       977 3. Crossveinless        716 4. Echinus, scute       681 5. Scute, crossveinless     8808 6. Scute, crossveinless, echinus         4 7. Echinus, crossveinless     1002 8. Wild type         1 20,765 Compare the recombination frequencies and speculate about the source of any apparent discrepancies in the recombination data.