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The UV dose that reduces a population of wild-type yeast cells to 37% survival is equivalent (assuming a Poisson distribution of hits) to the UV dose that causes an average of one lethal hit to each of the cells of the population. [18] The number of pyrimidine dimers induced per haploid genome at this dose was measured as 27,000. [18]
Excision repair cross-complementing rodent repair deficiency, complementation group 5 (xeroderma pigmentosum, complementation group G) is involved in excision repair of UV-induced DNA damage. Mutations cause Cockayne syndrome, which is characterized by severe growth defects, mental retardation, and cachexia.
For example, certain intensities of exposure to radioactive elements can inflict damage to an organism's genome, heightening rates of mutation. In humans, the appearance of skin cancer during one's lifetime is induced by overexposure to UV radiation that causes mutations in the cellular and skin genome. [107]
The 16 possible mutation types of the substitution class C>A are shown as an example. Once the mutation catalog (e.g. counts for each of the 96 mutation types) of a tumor is obtained, there are two approaches to decipher the contributions of different mutational signatures to tumor genomic landscape:
Nucleotide excision repair (NER) is a particularly important excision mechanism that removes DNA damage induced by ultraviolet light (UV). UV DNA damage results in bulky DNA adducts — these adducts are mostly thymine dimers and 6,4-photoproducts. Recognition of the damage leads to removal of a short single-stranded DNA segment that contains ...
These mutations arise due to chemical changes, the formation of cyclobutane pyrimidine dimers and photoproducts formed between adjacent pyrimidine bases. These mutations may be clinically related to specific signs of photoaging such as wrinkling, increasing in elastin and collagen damage. [5] [6] DNA UV mutation
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]
A UV radiation induced thymine-thymine cyclobutane dimer (right) is the type of DNA damage which is repaired by DNA photolyase. Note: The above diagram is incorrectly labelled as thymine as the structures lack 5-methyl groups.