a little something for Natalie...
http://albinism.org/publications/what_is_albinism.htmlI used the above website and a few other resources back in 2000 to do a report on albinism in reptiles for my English 218 (technical writing) course at NMSU.
One of the definitions I came across for the term albinism was, "the inability to properly produce the pigment melanin." Human examples would be people with full blown albinism, to people with hypopigmentation.
Leucism, unlike albinism, is the total reduction of all skin pigment, whether human or animal, and not just melanin.
Some additional reading:
http://en.wikipedia.org/wiki/Amelanistic ...
http://en.wikipedia.org/wiki/Albinism (they both redirect to the same page)
Wikipedia wrote:
Synonyms(lacking melanin): albinal, albinic, albinistic, albinoid, hypomelanistic, hypomelanoid, amelanistic, amelanoid
medterms.com wrote:
Albino: A person with albinism. The term was first applied by the Portuguese to people in West Africa who may have had partial or complete albinism. From the Latin albus for white. See also: Albinism.
Thusly, in this case albinism would make sense to associate it with just purely the word white as humans and many other mammals contain melanin as their primary, or solitary, skin pigment. In the case of reptiles and amphibians, as you've pointed out, they have multiple skin pigments that control various colors. As accurate as amelanistic is when describing a melanin-lacking reptile or amphibian, albino is also accurate as the term is routinely defined medically as the lack or no production of the pigment melanin. Thus albino=amelanistic=albino. Since albino is synonymous with lacking the pigment melanin, it is completely correct and accurate to utilize either term. The term amelanistic, for all intentive purposes, is somewhat of a cannibalized compound word with the root being melanin, the prefix being a- (a as a prefix means to lack, without) and the suffix -ic ( is like, pertaining to).
As for T+ and T-...it can be visually diagnosed, but as you stated it is more accurately diagnosed through testing.
Medical Dictionary @ TheFreeDictionary.com wrote:
albinism
Congenital anomaly due to a defect of melanin production as a result of one of several possible genetic defects. Oculocutaneous albinism type 1(OCA1) is due to a genetic defect in tyrosinase, the enzyme that metabolizes the amino acid tyrosine, which is essential for its conversion to melanin (formerly called tyrosinase-negative albinism). It is an autosomal recessive condition, which affects the skin, hair and eyes. The iris is a pale colour, the fundus and the pupil are reddish and the eye transilluminates markedly. There is poor visual acuity, photophobia, nystagmus and strabismus. Oculocutaneous type 2 (OCA2) is caused by a mutation of the OCA2 ('P') gene resulting in variable amounts of melanin synthesis. The hypopigmentation of the eyes, skin and hair varies from fair to normal (formerly called tyrosinase-positive albinism). It may be associated with the Hermansky-Pudlak syndrome in which there is albinism and easy bruising or bleeding. The other type of albinism is ocular albinism type 1 (OA1). It is inherited either as an X-linked or less commonly as an autosomal recessive trait. It affects mainly the eyes and in most instances males only and the skin colour is usually normal. Management involves full correction, possibly with tinted lenses. Surgery may be required for strabismus. See ocular fundus; inheritance; trans-illumination.
Albinism.org wrote:
While most people with albinism have very light skin and hair, not all do. Oculocutaneous (pronounced ock-you-low-kew-TAIN-ee-us) albinism (OCA) involves the eyes, hair and skin. Ocular albinism (OA), which is much less common, involves primarily the eyes, while skin and hair may appear similar or slightly lighter than that of other family members.
Over the years, researchers have used various systems for classifying oculocutaneous albinism. In general, these systems contrasted types of albinism having almost no pigmentation with types having slight pigmentation. In less pigmented types of albinism, hair and skin are cream-colored and vision is often in the range of 20/200. In types with slight pigmentation, hair appears more yellow or red-tinged and vision may be better. Early descriptions of albinism called these main categories of albinism “complete” and “incomplete” albinism. Later researchers used a test that involved plucking a hair root and seeing if it would make pigment in a test tube. This test separated “ty-neg” (no pigment) from “ty-pos” (some pigment). Further research showed that this test was inconsistent and added little information to the clinical exam.
Recent research has used analysis of DNA, the chemical that encodes genetic information, to arrive at a more precise classification system for albinism. Four forms of OCA are now recognized – OCA1, OCA2, OCA3 and OCA4; some are further divided into subtypes.
•Oculocutaneous albinism type 1 (OCA1 or tyrosinase-related albinism) results from a genetic defect in an enzyme called tyrosinase (hence ‘ty’ above). This enzyme helps the body to change the amino acid tyrosine into pigment. (An amino acid is a “building block” of protein.) There are two subtypes of OCA1. In OCA1A, the enzyme is inactive and no melanin is produced, leading to white hair and very light skin. In OCA1B, the enzyme is minimally active and a small amount of melanin is produced, leading to hair that may darken to blond, yellow/orange or even light brown, as well as slightly more pigment in the skin.
•Oculocutaneous albinism type 2 (OCA2 or P gene albinism) results from a genetic defect in the P protein that helps the tyrosinase enzyme to function. Individuals with OCA2 make a minimal amount of melanin pigment and can have hair color ranging from very light blond to brown.
•Oculocutaneous albinism type 3 (OCA3) is rarely described and results from a genetic defect in TYRP1, a protein related to tyrosinase. Individuals with OCA3 can have substantial pigment.
•Oculocutaneous albinism type 4 (OCA4) results from a genetic defect in the SLC45A2 protein that helps the tyrosinase enzyme to function. Individuals with OCA4 make a minimal amount of melanin pigment similar to persons with OCA2.
Researchers have also identified several other genes that result in albinism with other features. One group of these includes at least eight genes leading to Hermansky-Pudlak Syndrome (HPS). In addition to albinism, HPS is associated with bleeding problems and bruising. Some forms are also associated with lung and bowel disease. HPS is a less common form of albinism but should be suspected if a person with albinism shows unusual bruising or bleeding.
Lastly, albinos aren't always white (re: albus). In many instances of albino mammals, particularly dark skinned and haired species, they can actually have a yellowish cast to their hair and skin color; would they then be Xanthic instead of albino? Albino, amelanistic, tomaeto, tomaato, eether, iither....it's all semantics
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