Final answer:
A son affected by a genetic disorder is represented by a shaded square on a pedigree chart. Shading signifies possession of the trait, and squares represent males.
Step-by-step explanation:
On a pedigree chart, a son who is affected by a genetic disorder would be represented by a shaded square. The square symbolizes a male, and shading of the square indicates that the individual has the trait being traced. If the disorder is an X-linked recessive trait, a mother may pass the recessive allele to her son who then has a 50 percent chance of being affected, while daughters have a 50 percent chance of being carriers.