Question

Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight, and mutations to the dna in their skin cells are left uncorrected. why are the mutations not corrected in individuals with this disorder?

Answer 1

This disease is caused by mutations in 8 genes involved in DNA repair. Seven of these genes are involved in nucleotide excision repair. Some of the genes involved code for DNA polymerase, which is necessary for DNA replication with UV-induced damage.

The wavelength of ultraviolet light, which oscillates between 280 and 340 nm, induces a DNA or nucleotide lesion, under normal conditions the cells have the capacity to repair this damage, in people with this disease there is a defect in excision. Nucleotide repair by an alteration in the enzyme that is responsible for the repair of nuclear DNA in the course of mitosis.

Answer 2

People with xeroderma pigmentosum are extremely sensitive to UV light. this condition is caused by mutations affecting the nucleotide excision repair pathway, the genes involved, in the case of E. coli, are Uvr (A, B, C, D). mutants in genes are very sensitive to ultraviolet light, therefore, Uvr genes confer UV resistance, when this pathway doesn't work, thymine dimers and other forms of UV damage can't be repaired. People with xeroderma pigmentosum develop severe sunburns from just a few minutes in the sun, and about half will get skin cancer.