Xeroderma pigmentosum (XP) is a recessive genetic disease that occurs when one o
ID: 85374 • Letter: X
Question
Xeroderma pigmentosum (XP) is a recessive genetic disease that occurs when one or more of the genes that perform nucleotide excision repair are nonfunctional Why do XP patients have a much higher incidence of skin cancer than the general population? The mutation rate of all other genes is higher due to increased rates of thymine-dimer formation. The mutated nucleotide excision gene products increase cell proliferation. The mutation rate of all other genes is higher due to failure to repair. The mutated nucleotide excision gene products induce a higher mutation rate in other genes.Explanation / Answer
Answer : The mutation rate of all other genes is higher due to failure to repair.
Nucleotide excision repair is done when the normal DNA is damaged by UV rays which causes formation of pyrimidine dimers. The damage is first excised by endonucleases and then DNA polymerase repairs the missing sequence and ligase seals it.
When nucleotide excision repair is non-functional, the damaged DNA cannot be repaired.
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