Pedigree analysis here. Trait appears rarely, only when two parents by chance carry the hidden allele. X-linked Recessive . Father never passes on trait. X-linked Dominant .
Mother passes on to half of children.
Penetrance is the percentage of individuals with a genotype who actually show the trait. Expressivity is the degree of the trait. Gene product interaction In real living organisms, all traits result from the interaction of many gene products. Suppose two enzymes are required to produce a trait. The presence of recessive alleles at one locus makes useless the presence of dominant alleles at another locus.