A child who inherits one recessive gene will be healthy, but can pass on the disease to offspring. Genetic diseases are not contagious. With sex-linked traits, such as hemophilia, the defective gene is recessive and is only carried on the x chromosome. These traits occur mostly in boys because they have only one x chromosome.
Girls stand a chance of having a normal x gene to mask the defective x gene.
But mutations that change the gene's recipe can affect the reproduction of cells and may be connected to cancer.