Chapter 16.3, Problem 1TC

A team of phys clans treated four patients with breast cancer. Each patient received a course of chemotherapy (the same combination of drugs for each patient). In addition, researchers sequenced the genotype of cells in healthy skin tissue and in each patient's tumor at intervals during the treatment period. At the end of the course of treatment, all four patients were declared free of detectable cancer. But within 18 months, three of the patients had suffered a relapse. The researchers sequenced samples from the new tumors. If you compared the genetic information from the four patients, what kind of difference might you expect to find between the cured patient and the ones who suffered relapses? How might the theory of evolution by natural selection explain the difference?