. The word refers to a group of inherited conditions. People with have little or no pigment in their eyes, skin, or hair. Recently a test has been developed to identify carriers of the gene for ty-neg and for other types in which the tyrosianase enzyme does not function. The test uses a sample of blood to identify the gene for the tryrosinase enzymes by its code in DNA. The above test does not apply to to one type of , called X-linked ocular . For X-linked inheritance, the gene for is located on an X chromosome. Females have two X chromos ....