Suppose a female fly with normal eyes is crossed with a normal male.

Progeny include:
51 normal females
26 three-eyed males
27 normal males

What is the genotype of each of the parents?
Is the three-eyed trait dominant or recessive?
Is it X-linked?

2.  Explain these pedigrees:

Inherited Parkinson's -- Iceland

3.  Arizona X-linkage Problems