Albinisim essay

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  • Topic: Albinism, Melanin, Dominance
  • Pages : 7 (2415 words )
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  • Published : April 24, 2013
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Albinism
Albinism is a congenital disorder where there is a complete or partial absence of pigment in the skin, hair, and eyes because of the absence or defect in the enzyme that produces melanin. Melanin is responsible for pigment in plants, animals, and protists. Albinism in man has been described by many Greek and Roman writers, and the first accurate scientific paper about it was written in 1908 by Sir Archibald Garrod. Most people only think of humans in the case of albinism, but in reality, it affects humans as well as plants and animals.

In plants, Albinism is the total or partial absence of chlorophyll. Because there is an inadequate amount of chlorophyll, photosynthesis is impaired. As a result, plants with albinism usually die at a young age. According to scientific authors Maya Kumari, Heather J. Clarke, Ian Small, and Kadambot H. M. Siddique, some environmental conditions like temperature, light, media composition, and culture conditions can play a role in determining the frequency of albino plant formation. Although environmental factors can sometimes play a role, genetic factors are the main determinants. Genetic studies in different crops show that it is a recessive trait governed by many loci. Because nuclear as well as chloroplast genomes affect albinism, incompatibilities between them is a likely cause of pigment defects in hybrid progenies (Kumari). In angiosperms large amounts of these incompatibilities are found. Unfortunately, there is no solution for albinism in plants. Although there is no solution, it has been defeated in some species through somatic hybridization and development of cybrids (Kumari).

As in plants, albinism in animals, though rare, occurs when there no melanin produced. About one in ten thousand mammal births a year are albino. It is the most common in birds, occurring one in one thousand seven hundred sixty-four times. The melanin is the pigment that determines that color of the animal’s skin, fur, and eyes. Most albino animals are pure white, but not all. Some traits allow some pigment to appear on the animal. Vice versa, all pure white animals are not albino. The difference between pure white animals with and without albinism is the eyes. Melanin affects the development of eyes, and without the dark brown or red-yellow pigments in the iris, albino animals have pink or pale blue eyes. If an animal is pure white but has dark or normal colored eyes, that animal is not an albino; it is leucistic.

Melanin has two color ranges: eumelanin and pheomelanin. Eumelanin are dark browns and black pigments, and pheomelanin are red, tan, and blonde pigments. In animals, these two ranges help make up cryptic coloration, or camouflage. It serves two purposes. One purpose of melanin is to protect the animal from the sun. Animals have melanosomes, or clusters of melanin, that help block harmful sunrays and allow passage of beneficial ones. Another purpose of melanin is vision. It helps develop the retina, iris, optic nerves, and eye muscles. Because albino animals lack melanin, they cannot blend into their surroundings. They also tend to have poor eyesight and vision problems.

The production of melanin is very complex. It is made in a chain of chemical reactions that occur in melanocyte, a specialized cell. The enzyme tyrosinase is the most important factor in the production of melanin. Without tyrosinase, melanin cannot be made, and the animal will be albino.

Since albinism is hereditary, the genes are inherited from the parents. Mammals have a gene called the TYR gene that determines the existence of tyrosinase. Animals with albinism suffer from a damaged TYR gene, which causes an unreliable production of melanin. Pure white, light eyed albino animals have a TYR gene that does not function, resulting in no tyrosinase production and no pigmentation. In other albinos the TYR gene allows some tyrosinase and causes melanin to increase as the animal...
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