Biochemistry of Nutrition Assignment Example | Topics and Well Written Essays - 500 words

Biochemistry of Nutrition - Assignment Example The mechanisms included in DNA tolerance are a replicative bypass of template damage with gap formation and translesion DNA synthesis. This paper attempts to throw light on DNA repair by direct repair mechanisms. The major source of base damage upon exposure to UV radiation at wavelengths near absorption maximum of DNA is the production of photo products such as cyclobutane pyrimidine dimers and 6-4 pyrimidine-pyrimidones. The photoproducts mediate DNA damage by posing serious threats to viability and functional integrity of cells by interfering with vital processes including DNA replication and transcription. The reversal of DNA damage through photoreactivation is a mechanism that involves the repair of photoproducts. The light-dependent process reverses DNA damage through monomerization of cis-syn-cyclobutyl pyrimidine dimers. Furthermore, the trans-syn-cyclobutyl pyrimidine is also repaired through the light-dependent repair process. The process involves the formation of a DNA complex with photoreactivating enzyme. The complex absorbs light (>300nm) which causes the repair of the damaging photoproducts after which the native DNA is restored after the release of photoreactivating enzyme. The depletion of one or more nutrients results in sporulation in Bacillus subtilis. A spore product called thyminyl-thymine adduct is formed when Bacillus subtilis is exposed to UV radiation at ~240nm. The repair of spore photoproduct occurs during early germination and is mediated through the SP-specific repair process. Furthermore, spore photoproducts are also repaired through nucleotide excision repair system. The formation of O6-Methylguanine occurs as a result of damage caused by the presence of alkylating agents such as N-methyl-N-nitrosoguanidine.