What type of allele is often detected as a distortion in segregation ratios, where one class of expected progeny is missing?

Duchenne muscular dystrophy is caused by a recessive X-linked allele. A male with this disorder:

What term describes the phenomenon when the expression of one gene masks the expression of another?

In a plant species, if the B allele (blue flowers) and the b allele (white flowers) are incompletely dominant (Bb is light blue), what offspring ratio is expected in a cross between a blue-flowered plant and a white-flowered plant? 

A pleiotropic gene

A cross between two short-tailed mice results in offspring in the ratio of 2/3 short-tailed and 1/3

If two Drosophila strains with the same autosomal recessive mutant phenotype of short bristles are crossed together and all the progeny are wild type, indicate which of the two possibilities below is correct.

What possible genotype(s) could an individual of blood type A have? Select all that apply from the list below.

If a mother has type A blood and their son has type O blood, what are the possible blood types of the father, if there are not additional genetic interactions occurring?