Which statement best describes cancer cells?
A They grow as a single layer of cells.
B They cease to reproduce after 20-50 mitotic divisions.
C They reproduce only when needed to replace missing cells.
D They are not regulated by contact inhibition.
The Correct Answer and Explanation is :
The correct answer is D: They are not regulated by contact inhibition.
Explanation:
Cancer cells are characterized by their uncontrolled growth and division, which distinguishes them from normal cells. In normal tissues, cells typically grow in a single layer and stop dividing when they come into contact with neighboring cells, a phenomenon known as contact inhibition. This regulatory mechanism ensures that tissues maintain proper structure and function by preventing overcrowding.
However, cancer cells exhibit a lack of contact inhibition. They continue to divide and grow even when they are in close proximity to other cells. This unchecked proliferation is a hallmark of cancer and contributes to tumor formation. Unlike normal cells, which may cease to divide after a certain number of mitotic divisions (often around 20 to 50 divisions, due to telomere shortening), cancer cells can bypass these limitations. They often achieve this through mechanisms such as activating telomerase, an enzyme that maintains telomere length, allowing them to divide indefinitely.
Moreover, cancer cells do not reproduce solely in response to the body’s needs for replacing lost or damaged cells. Instead, they grow and divide independently of the body’s regulatory signals. This unregulated growth can lead to the formation of tumors, which can invade nearby tissues and spread to distant sites in the body, a process known as metastasis.
In summary, cancer cells are marked by their lack of regulation, particularly in relation to contact inhibition. Their ability to proliferate uncontrollably is a fundamental characteristic that underlies the development and progression of cancer, making them distinct from normal, healthy cells. This difference is crucial for understanding how cancer develops and for developing effective treatments.