[Campbell Biology P.377] A child is diagnosed with Xeroderma Pigmentosum XP , an inherited d... | Practice Question

A child is diagnosed with Xeroderma Pigmentosum XP , an inherited disorder. Based on the information provided, what is the most direct consequence of this disorder regarding DNA repair, and what would be a crucial protective measure for this child?

  • A: Defective DNA ligase activity, leading to stalled replication forks; crucial measure is dietary supplements.
  • B: Inability to repair thymine dimers caused by UV radiation, resulting in high risk of skin cancer; crucial measure is strict sun protection.
  • C: Defective telomere replication, leading to premature cell aging; crucial measure is gene therapy.
  • D: Impaired proofreading by DNA polymerase, leading to increased mutation rates; crucial measure is antibiotic treatment.

Explanation

The text clearly states that Xeroderma Pigmentosum XP is caused by an inherited defect in a nucleotide excision repair enzyme, leading to uncorrected mutations in skin cells caused by ultraviolet light, which often results in skin cancer. Therefore, strict sun protection is a crucial measure for individuals with XP.