Albinism :: essays research papers

Albinism     The word "albinism" refers to a group of inherited conditions. Peoplewith albinism have little or no blusher in their eyes, skin, or hair. They haveinherited elements that do not make the usual amounts of a pigment called melanin.One person in 17,000 has some token of albinism. Albinism affects people from allraces. Most children with albinism are born to parents who have normal hair andeye color for their ethnic backgrounds. Albinism is found on the eleventhchromosome, portion q, loci 14-21.Oculocutaneous albinism involves the eyes, hair, and skin. Ocular albinisminvolves primarily the eye. People with ocular albinism may have slightlightening of hair and skin colors as well, compared to other family members. At march researchers have found 10 different types of oculocutaneous albinism,and five types of ocular albinism. Newer laboratory research studying DNA hasshown that there are numerous types of changes in the genes of those withalbi nism, including inwardly families.The most common types of oculocutaneous albinism are called "ty-negative"and "ty-positive". Persons with ty-negative albinism have no melaninpigmentation, and more difficulty with vision. Those with ty-positive albinismhave very slight pigmentation, and generally less severe visual difficulties.Tests were make on the hair roots of individuals with albinism, to tell thesetypes of albinism apart. However, these hair tests cannot identify types ofalbinism, particularly in young children, whose pigment systems are immature.Therefore hair tests are not helpful in predicting the extent of visualdisability of a child.     "Ty-Neg" (also called Type 1A) albinism results from a genetic defect inan enzyme called tyrosinase. Tyrosinase helps the body to change the amino deadlytyrosine into pigment. The genetic defect that causes albinism in other types ofalbinism is unknown, but it is speculated that it involves o ther enzymes used tomake pigment.     Albinism is passed from parents to their children through genes. Fornearly all types of albinism both parents must carry an albinism gene to have achild with albinism. Parents may have normal pigmentation but still carry thegene. When both parents carry the gene, and neither parent has albinism, thereis a one in four chance at each pregnancy that the baby will be born withalbinism. This type of inheritance is called autosomal recessive allele inheritance.     If a parent has a child with albinism, it means the parent must carrythe albinism gene. Until recently, unless a person has albinism or has a childwith albinism, there was no way of knowing whether he or she carries the gene