Question

Statement I: Proto oncogenes have been identified in normal cells.

Statement II: Proto oncogenes could lead to oncogenic transformation of the cells if activated.

• A. Both the statements I and II are correct
• B. Both the statements I and II are incorrect
• C. Statement I is incorrect and statement II is correct
• D. Statement I is correct and statement II is incorrect

Answer 1

The correct option is A Both the statements I and II are correct

The cellular oncogenes (c-onc) or proto-oncogenes have been identified in normal cells. The proto-oncogene acts as a positive growth regulator, and is involved in promoting the differentiation and proliferation of normal cells.

However, these genes undergo mutations. The mutant, cancer-promoting forms of proto-oncogenes are referred to as oncogenes. Oncogenes cause the transformation of normal cells to cancerous cells.

The cancerous cells divide uncontrollably to form a mass of cells called tumors.

A tumour is classified into following types based on its ability to undergo metastasis (spreading):

• Benign tumor - These tumours are localized at a particular location in the body and do not spread to the other parts of the body. Such tumors are generally harmless.
• Malignant tumor - These tumours are cancerous and they will grow quickly and spread to other normal tissues of the body. This ability to spread is called metastasis.

Hence, proto-oncogenes are present in all normal cells and could lead to oncogenic transformation of the cells if activated.