What is the fine-grained topic of the following text: Genetic linkage analyses of several hundred phenotypically defined F2 progeny from reciprocal crosses between the ACI and COP or BN strains revealed a total of seven genetic determinants of susceptibility to E2-induced mammary cancer on chromosomes 2, 3, 4, 5, 6, 7 and 18. Only return the topic.
Genetic determinants of susceptibility to E2-induced mammary cancer