Question

6. What is cancer? In your answer, discuss how a normal cell differs from a cancer cell, including specific examples regarding differences in the cell cycle.

Answer 1

Cancer is a disease that has killed millions of people all over the globe. In our body the differentiation of normal cells is highly controlled but however in cancer cells there the regulatory mechanisms are lost. Normal cells have the property of contact inhibition which inhibits the uncontrolled growth of cells by means of contact with other cells. This property is absent in cancer cells as a result they continue to divide forming masses of cells called tumors.

There are two types of tumors:

• Benign tumor: They normally remain confined to the region of its formation and does not cause much damage.
• Malignant tumor: They grow very rapidly affecting surrounding normal cells. Cells from such tumors reach distant sites through the blood and get lodged in the body and form a new tumor there. This property is called metastasis and is a very feared property of malignant tumors. Malignant tumors are responsible for cancer.

Transformation of normal cells into cancerous cells may be due to physical, chemical or biological agents which are called carcinogens. X rays, gamma rays, UV radiations can transform normal cells into cancerous cells. There are also cancer causing viruses called oncogenic viruses which have genes called viral oncogenes. Normal cells also have numerous genes called cellular oncogenes which when activated can lead top cancerous transformation of cells.

Chemical carcinogens present in tobacco smoke is a major cause of lung cancer.