Identify which of the following statements about cancer are incorrect:
(A) Cancerous cells show a property of contact inhibition.
(B) Metastasis is the most feared property of malignant tumors.
(C) Benign tumors can spread to distant sites through the blood.
(D) Non-ionizing radiation can also cause cancer.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A and C only
Normal cell growth is tightly controlled. In cancer cells this control breaks down, and the cells form masses called tumours. Benign tumours stay where they started. Malignant tumours grow fast, invade nearby tissue and spread.
(A) Cancerous cells show a property of contact inhibition. — An incorrect statement. Normal cells show contact inhibition: touching other cells stops their growth. Cancer cells have lost this property, so they keep dividing.
(B) Metastasis is the most feared property of malignant tumors. — A correct statement. In metastasis, cells from a malignant tumour reach distant sites through the blood and start new tumours there.
(C) Benign tumors can spread to distant sites through the blood. — An incorrect statement. Benign tumours remain confined to their original place and do not spread. Spread through blood is a feature of malignant tumours.
(D) Non-ionizing radiation can also cause cancer. — A correct statement. Non-ionising radiation such as UV damages DNA and can turn normal cells into cancer cells, just as X-rays and gamma rays do.
NCERT Extract:
Cancer – “… 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. Tumors are of two types: benign and malignant. Benign tumors normally remain confined to their original location and do not spread to other parts of the body and cause little damage. … Cells sloughed from such tumors reach distant sites through blood, and wherever they get lodged in the body, they start a new tumor there. This property called metastasis is the most feared property of malignant tumors.”
Causes of Cancer – “… Ionising radiations like X-rays and gamma rays and non-ionizing radiations like UV cause DNA damage leading to neoplastic transformation.”