Read the given passage carefully and answer the questions.
Salmonella typhi is a pathogenic bacterium which causes typhoid fever in human beings. Sustained high fever (39° to 40°C), weakness, stomach pain, constipation, headache and loss of appetite are some of the common symptoms of this disease. Typhoid fever could be confirmed by Widal test. Plasmodium enters the human body as sporozoites. The parasites initially multiply within the liver cells and then attack the red blood cells (RBCs) resulting in their rupture. The rupture of RBCs is associated with release of a toxic substance, haemozoin, which is responsible for the chill and high fever recurring every three to four days. There is lymphoid tissue also located within the lining of the major tracts (respiratory, digestive and urogenital tracts) called mucosa-associated lymphoid tissue (MALT). In our body, cell growth and differentiation is highly controlled and regulated. In cancer cells, there is breakdown of regulatory mechanisms. Normal cells show a property called contact inhibition by virtue of which contact with other cells inhibits their uncontrolled growth. Cancerous cells just continue to divide giving rise to masses of cells called tumors. Tumors are of two types: benign and malignant. Cannabinoids are a group of chemicals, which interact with cannabinoid receptors present principally in the brain. Generally taken by inhalation and oral ingestion, these are known for their effects on cardiovascular system of the body.
Which one of the following statements is not true?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Normal cells do not show the property of contact inhibition.
Contact inhibition is the property by which a cell stops growing when it touches other cells. It keeps normal cell growth under control.
Option (1) Cancerous cells lose the property of contact inhibition. — A true statement. In cancer cells the regulatory mechanisms break down. Cancer cells have lost contact inhibition, so touching other cells does not stop them.
Option (2) Normal cells do not show the property of contact inhibition. — Not a true statement. The fact is the other way round. Normal cells do show contact inhibition; contact with other cells stops their uncontrolled growth. Two small words, ‘do not’, were all NTA needed to turn a line of the book false. Check every word against what the book says.
Option (3) Cancerous cells show uncontrolled growth. — A true statement. Without contact inhibition, cancerous cells just continue to divide. They form masses of cells called tumors.
Option (4) Benign tumors normally remain confined to their original location. — A true statement. A benign tumor stays where it began, does not spread to other parts of the body and causes little damage. A malignant tumor, by contrast, spreads to new sites through the blood (metastasis).
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.