Genetic Testing for Cancer Susceptibility — NEET Biology

Correct answer: C — S1, S3 and S5 only

Let's evaluate each statement: S1: Cancer-causing viruses called oncogenic viruses have genes called viral oncogenes. These are classified as biological agents (carcinogens). Thus, S1 is correct. S2: The chemical carcinogens present in tobacco smoke have been identified as a major cause of lung cancer. However, UV rays are classified as *non-ionizing* radiations, not ionizing radiations. Ionizing radiations include X-rays and gamma rays. Thus, S2 is not correct. S3: Several genes called cellular oncogenes (c-onc) or proto-oncogenes have been identified in normal cells which, when activated under certain conditions, could lead to oncogenic transformation of the cells. Thus, S3 is correct. S4: Physical carcinogens include ionising radiations like X-rays and gamma rays and non-ionizing radiations like UV. These cause DNA damage leading to neoplastic transformation. They do not necessarily lead to cancer by directly binding to specific receptors on cell surfaces; their primary mechanism is DNA damage. Also, the quantifier 'All' makes the statement incorrect. Thus, S4 is not correct. S5: Techniques of molecular biology can be applied to detect genes in individuals with inherited susceptibility to certain cancers. Identification of such genes can be very helpful in prevention of cancers, as such individuals may be advised to avoid exposure to particular carcinogens. Thus, S5 is correct. Based on the analysis, S1, S3, and S5 are correct. Therefore, option A is the correct answer. NCERT core concept: Understanding different types of carcinogens (physical, chemical, biological), the role of oncogenes (proto-oncogenes and viral oncogenes) in cancer development, and strategies for cancer prevention.