Dr. ANJU BATTA SEHGAL
Albinism is a rare genetic condition caused by mutations of certain genes which affect the production of Melanin in our body; it controls the pigmentation (colour) of your skin, eyes and hair. People with albinism have extremely fare skin, white eyes and hair. Term albinism refers to oculocutaneous albinism (OCA). OCA is a group of disorders passed down in families where the body cannot make pigment melanin. It’s the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and pink or blue eyes, organisms with this condition are referred to as albinos.
Oculocutaneous albinism (OCA) is a clearly defined set of seven types of genetic mutations which reduce or completely prevent the synthesis of eumelanin or pheomelanin, resulting in reduced pigmentation, Type I oculocutaneous albinism (OCA1a) is the form most commonly recognised as ‘albino’ as this results in a complete absence of melanin in the skin, hair/fur/feathers, and pink pupils. Melanin normally protects the DNA of skin cells from the damaging effects of UV radiations of sunlight, presence of melanin is essential for developing eyes for proper eyesight.
In 1900, Ales Hrdlieka, an anthropologist and physician working in American Museum of Natural History, visited Hopi Villages of Black Mesa area and reported a startling discovery. Among these native Americans he noticed the condition called albinism. Black Mesa is the ancestral home of Hopi Native tribes of north eastern Arizona. Genetic basis of albinism was first described by English physician Archibald Garrod, who noticed in 1908 that this condition was inherited as an autosomalrecessive trait. Meaning that a person must receive two copies of albino mutations, one mutated gene from each parent. Recent findings report that albinism is the result of defects in any one of several genes that control the synthesis and storage of melanin: many different types of mutations can occur at each gene. The Hopi’s show oculocutaneous albinism type2, due to defect in OCA2 gene on chromosome 15.
Albinism has been reported in all different ethnic groups and is described in ancient writings since the beginnings of humankinds. However most of the groups show 1 in 20000 frequency but Hopi natives show 1 in 200, hundred times more frequent than others. The reason of high frequency was the Hopi culture itself. They consider their members as important, clean, intelligent and special. Having more number of people with albinism in their community was considered good sign by them. Inbreeding in the community led to the pure blood in Hopi’s. They used to get special treatment in everyday activities too. They made small garden plots at the foot hills of Black Mesa. But the male Hopis with albinism were excused of this labour and allowed to remain behind in the village with the women of the tribe, performing other duties. Special considerations given to them allowed them to avoid the detrimental effects of albinism—increased skin cancer and poor eye sight.
Melanin is an organic pigment that produces most of the colour seen in mammals. Depending on how it is created, melanin comes in two colour ranges, eumelanin (producing dark browns and blacks) and pheomelanin (producing light reddish tans and blondes). The dark and light Melanin have their influence either alone or in conjunction, making plain or multi-coloured coverings/ skins. Sometimes, also in a special condition called agouti which makes multi-coloured individual hairs. Production of melanin occurs in melanocytes in a complex process involving the enzyme tyrosinase.
Mammals have a gene that codes for the presence of tyrosinase in cells – called the TYR gene. If this gene is altered or damaged, melanin cannot be reliably produced and the mammal becomes an albino.Along with this TYR gene, several other genes can cause albinism. This is because other hormones and proteins are also involved in melanin production, the presence of which is genetically determined. In mice, a total of 100 genes are known to affect albinism.
However two parents with albinism can have an unaffected child. This happens when the parents carry mutations in different genes that are involved in the production of pigment and this is an example of a phenomenon called genetic complementation. Unfortunately, people with this genetic conditions, in many societies are often subject to discrimination and prejudice.
(The author is former Principal NSCBM Govt. College Hamirpur, Himachal Pradesh and former Professor of Botany)
