Genetic disorders, affecting many different races and genders, have been around for a very long time. Genetic disorders, usually caused by recessive genes, range from minor traits to conditions that prove fatal. Moreover, disorders often result in multiple abnormalities. Furthermore, skeletal and muscular disorders are often transmitted by a single gene, like achondroplasia, a type of dwarfism characterized by abnormal proportions of the arms, legs and body, results from impaired cartilage growth. Achondroplasia is a birth defect that is familial, passed on from one generation to the next. This genetic defect of the cartilage cells affects only some of the cartilage in the body, like the spine and limbs.
Often those people who suffer from the condition typically have a normal size trunk with a painful, curved spine, a relatively large head, and short arms and legs. As has been pointed out achondroplasia, passed on from one generation to the next, is a defect often transmitted by a single gene. Likewise, albinism, absence of pigment in skin, hair, and eyes, is a genetic birth defect passed on from one generation to the next. Albinism is generally considered to be the first genetic disorder ever recognized. References to it have been found as far back as the Old Testament. Members of any race can be albinos, and other creatures can also inherit this inability to manufacture color pigments.
In humans albinism is caused by a recessive gene. If two carriers of the albinism gene produced children, chances are one in four that they will have a child who is albino. Often the eyes appear to be pink, because the color of blood can be seen through the iris. Albino hair is light yellow to white, and the skin is as white as milk. Because of their lack of pigmentation their skin is easily sunburned and their eyes need to be protected from strong sunlight. The gene that causes albinism was discovered in 1990.
The defective gene is found on chromosome 11, and results in a deficiency known as tyrosinase. Tyrosinase is necessary for the production of melanin. Screening and prenatal diagnosis have become possible; however, there is no treatment for the correction of albinism.