Question

What is the effect of light on body pigmentation?

Answer 1

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The effect of light on body pigmentation of the animals which live in regions of low intensity of light such as caves have less pigmentation than that of animals exposed to light .

For example a cave dwelling amphibian properties and givens has coloured skin because of less pigmentation when it is brought into sunlight the colour turns dark .

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Answer 2

Explanation:

1. Human skin interfaces between the body and external environment, acts as a barrier against physical, chemical and biological attacks from the environment.
2. Exposure to solar radiation and sun sensitivity are associated with increased risk for skin cancers (1, 2).
3. The incidence of skin cancer (including melanoma and non-melanoma skin cancers) has been increasing substantially in the United States (3, 4).
4. Solar UV radiation induces genotoxic effects by damaging wide variety of bio-organic molecules including DNA, proteins and other small molecules such as folate.
5. Biological macromolecules or small compounds present in the skin act as chromophores and absorb radiation of specific wavelength to bring about a cascade of reactions within the cell.
6. Nucleic acid, urocainic acids, co-factors NADPH and NADH, aromatic amino acids- tryptophan and tyrosine, riboflavins, porphyrins and melanins and their precursors are all chromophores present in the skin.
7. They absorb protons and undergo a series of structural and chemical changes (5).
8. Melanin synthesized in the melanocytes plays an important role in protecting the skin from radiation-induced damage.
9. Melanocytes transfer melanosomes to keratinocytes, where melanin is localized above the nucleus in the form of a cap like structure to protect the cellular DNA (6).
10. UV radiation induces immediate pigment darkening (IPD) by chemical modification of melanin, and possibly spatial redistribution of melanosomes in keratinocytes and melanocytes (7).
11. UV exposure also leads to delayed tanning (DT) by new synthesis of melanin over several days after UV exposure and persists for weeks (8).
12. UV-induced pigmentation is thought to play a protective role by preventing DNA damage and accumulation of mutations.
13. Given the importance of melanin and skin pigmentation in providing protection from solar radiation, the evolutionary aspects of human skin pigmentation have received much attention.
14. Skin pigmentation is thought to have evolved as protective adaptation from the damaging effects of direct exposure of the skin to solar radiation (9).
15. However, since melanin pigment absorbs solar radiation, which is required for synthesis of vitamin D in the skin, the primary site of production of this molecule essential for a wide range of physiological processes, loss of dark pigmentation and evolution of fair skin, in order to maximize the absorption of solar radiation for vitamin D synthesis (10) but while simultaneously increasing the susceptibility to its damaging effects, is thought to be the evolutionary price of migration of early humans to higher latitudes.
16. This review provides an overview of the current knowledge on the biological mechanisms of the effects of solar radiation on melanocytes, melanin and human skin pigmentation.