Read the passage and answer the following questions:
Cancer is one of the most dreaded diseases of human beings and is a major cause of death all over the globe. More than a million Indians suffer from cancer and a large number of them die from it annually. The mechanisms that underlie development of cancer or oncogenic transformation of cells, its treatment and control have been some of the most intense areas of research in biology and medicine. In our body, cell growth and differentiation is highly controlled and regulated. In cancer cells, there is breakdown of these regulatory mechanisms. Normal cells show a property called contact inhibition by virtue of which contact with other cells inhibits their uncontrolled growth. Cancer cells appears to have lost this property. As a result of this, cancerous cells just continue to divide giving rise to masses of cells called tumors.
Which among the following is the cause of cancer?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → All of these.
Agents that change normal cells into cancer cells are called carcinogens. They can be physical, chemical or biological. Radiations are physical carcinogens. They damage DNA, and the damaged cells may turn into cancer cells.
Option (1) X-rays. — Incorrect. X-rays are ionising radiations. They can damage DNA and cause cancer, but they are only one of the causes listed here.
Option (2) Gamma rays. — Incorrect. Gamma rays are also ionising radiations that damage DNA. They are one cause, but not the only one in the options.
Option (3) UV rays. — Incorrect. UV rays are non-ionising radiations, yet they too cause DNA damage that can lead to cancer. Again, this is only one of the causes.
NCERT Extract:
Cancer – “… Causes of cancer : Transformation of normal cells into cancerous neoplastic cells may be induced by physical, chemical or biological agents. These agents are called carcinogens. Ionising radiations like X-rays and gamma rays and non-ionizing radiations like UV cause DNA damage leading to neoplastic transformation. The chemical carcinogens present in tobacco smoke have been identified as a major cause of lung cancer.”