Name Two Molecules in the Body That Uv Radiation Can Damage

Solar ultraviolet radiations (UV) exposure triggers DNA damage, a preliminary step in the process of carcinogenesis.

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The stability of DNA is extremely of import for the proper performance of all cellular processes. Exposure to UV radiation alters the structure of Dna, affecting the physiological processes of all living systems ranging from leaner to humans.

Ultraviolet Radiation

Natural sunlight stimulates the production of vitamin D, an of import food for the formation of healthy basic. Yet, sunlight is also a major source of UV radiations. Individuals who get excessive UV exposure are at a great risk of developing skin cancers. There are three types of UV rays: UVA, UVB and UVC.

• UVC rays (100-280 nm) are the most energetic and dissentious of the three rays. Fortunately, UVC is captivated by the ozone layer before reaching the earth'southward surface.
• UVA rays (315-400 nm) possess the lowest free energy and is able to penetrate deep into the pare. Prolonged exposure has been linked to ageing and wrinkling of the pare. UVA is too the main cause of melanomas.
• UVB rays (280-315 nm) possess higher energy than UVA rays and affect the outer layer of the skin leading to sunburns and tans. Basal cell carcinoma and squamous cell carcinoma are caused by UVB radiation.

DNA Harm by UV Radiation

DNA is composed of two complementary strands that are wound into a double helix. The hereditary message is chemically coded and made up of the four nucleotides adenine (A), thymine (T), guanine (Thousand) and cytosine (C).

UVB light interferes direct with the bonding between the nucleotides in the DNA. The two main DNA lesions formed by exposure to UVB are cyclobutane pyrimidine dimers (CPD) and 6-four pyrimidine pyrimidone photoproducts (6-4PPs), and its Dewar isomers.

CPDs are formed when two side by side pyrimidine  bases (thymine –TT or cytosine – CC) get covalently linked producing a cyclic ring structure. 6-4PPs result from a single covalent bond formed between the 5' end of C6 and three' end of C4 of adjacent pyrimidines. This leads to the formation of an unstable oxetane or azetidine intermediate depending on whether the three' end base is a thymine or cytosine.

Subsequent spontaneous rearrangement of these intermediates gives ascent to 6-4PP. The pyrimidine dimers cause a kink in the DNA backbone, halting transcription and poly peptide synthesis. 6-iv pyrimidine pyrimidone adducts undergo isomerization to their Dewar form upon exposure to another photon of lite from UVB or UVA radiation. The most mutual mutation induced by UVB is C to T transversion. Double base of operations substitutions (CC to TT) besides occur, albeit less frequently.

UVA (and also UVB) radiation cause indirect damage to DNA via absorption of photons by non-Deoxyribonucleic acid chromophores. This generates reactive oxygen species similar singlet oxygen or hydrogen peroxide that oxidize the Dna bases causing mutations. The most common mutation is the 1000-T transversion wherein guanine gets oxidized into 8-oxo- 7,8-dihydroguanine (8-oxoG) hindering its pairing with cytosine. During the replication process, 8-oxoG pairs with adenine. When the second strand is synthesized, 8-oxoG is replaced with a thymine leading to a Thou-T transversion.

The importance of wearing sunscreen explained

DNA Repair

The genetic lesions produced by UV radiations are ofttimes repaired soon subsequently they are formed, through a process called nucleotide excision repair. A nuclease enzyme recognizes and removes a segment of Dna containing the lesion. Then, the polymerase inserts the right bases and ligase seals the gap. However, if unrepaired lesions accumulate or the repair machinery is faulty, it can pb to prison cell death, mutagenesis and even cancer.

Sources:

• Sinha RP, Häder DP "UV-induced DNA damage and repair: A review." Photochem Photobiol Sci. 2002 Apr; one(4):225-36. Review
• Rastogi RP, Richa, Kumar A, Tyagi MB and Sinha RP "Molecular mechanisms of ultraviolet radiations-induced DNA damage and repair." J Nucleic Acids. 2010 Dec 16;2010:592980. doi: 10.4061/2010/592980
• Ravanat JL, Douki T and Cadet J "Direct and indirect effects of UV radiation on Deoxyribonucleic acid and its components." J Photochem Photobiol B. 2001 Oct;63(one-3):88-102. Review

Further Reading

• All Dna Content
• What is DNA?
• Dna Properties
• DNA Chemical Modifications
• Dna Biological Functions

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Source: https://www.news-medical.net/life-sciences/The-Mechanism-of-DNA-Damage-by-UV-Radiation.aspx

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