20. Conversion of proto-oncogene to oncogene may involve the following processes:
    A. mutation in coding sequence
    B. gene amplification
    C. chromosome rearrangement
    D. mutation in non-coding sequence
    Which one is appropriate?

Final Answer

The appropriate processes involved in the conversion of a proto-oncogene to an oncogene are:

A. Mutation in coding sequence
B. Gene amplification
C. Chromosome rearrangement

Explanation

Proto-oncogenes are normal genes that regulate cell growth and division. Their conversion to oncogenes—genes that promote uncontrolled cell proliferation—occurs through various genetic alterations:

• Mutation in coding sequence (A): Point mutations or insertions can alter the protein structure, resulting in a hyperactive or constitutively active protein that drives cancerous growth.

• Gene amplification (B): Multiple copies of the proto-oncogene increase the production of the encoded protein, enhancing its effect on cell division.

• Chromosome rearrangement (C): Translocations or inversions can misplace proto-oncogenes near strong promoters or create fusion genes with new oncogenic properties.

A mutation in the non-coding sequence (D) alone usually does not directly convert proto-oncogenes to oncogenes, unless it affects regulatory regions that increase expression, but this is less direct and not classically considered a primary mechanism.

Thus, A, B, and C are the main recognized mechanisms actively involved in oncogene activation.