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This process of absorption works to reduce the risk of DNA damage and the formation of pyrimidine dimers. UVA light makes up 95% of the UV light that reaches earth, whereas UVB light makes up only about 5%. UVB light is the form of UV light that is responsible for tanning and burning. Sunscreens work to protect from both UVA and UVB rays.
Xeroderma pigmentosum (XP) is a genetic disorder in which there is a decreased ability to repair DNA damage such as that caused by ultraviolet (UV) light. [1] Symptoms may include a severe sunburn after only a few minutes in the sun, freckling in sun-exposed areas, dry skin and changes in skin pigmentation. [1]
This disease can cause light-skin, extreme freckling and facial lesions, as well as preventing the repair of pyrimidine dimers. Diagnosis of this disease is done by measuring the enzyme's level in white blood cells in a blood sample. Symptoms in children include extreme UV sensitivity, excessive freckling, multiple skin cancers and corneal ...
In Canadian women, the upper chest is commonly affected. [9] Spider veins on face and neck; Loss of color and fullness in lips; Symptoms of photoaging attributed to prolonged exposure to UV: Wrinkles deepen and forehead frown lines can be seen even when not frowning. Telangiectasias (spider veins) most commonly seen around the nose, cheeks and ...
Blood levels of folate, a nutrient vital for fetal development, can be degraded by UV radiation, [57] raising concerns about sun exposure for pregnant women. [58] Lifespan and fertility can be adversely affected for individuals born during peaks of the 11-year solar cycle , possibly because of UV-related folate deficiency during gestation.
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Monoadduct damage cause by change in single nitrogenous base of DNA; Di adduct damage; Damage caused by exogenous agents comes in many forms. Some examples are: UV-B light causes crosslinking between adjacent cytosine and thymine bases creating pyrimidine dimers. This is called direct DNA damage. UV-A light creates mostly free radicals.
Patients with systemic lupus erythematosus experience skin symptoms after sunlight exposure; some types of porphyria are aggravated by sunlight. A rare hereditary condition xeroderma pigmentosum (a defect in DNA repair) is thought to increase the risk of UV-light-exposure-related cancer by increasing photosensitivity.