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Oncogenes are altered versions of normal genes called proto-oncogenes. They promote cell growth and division in an uncontrolled manner, leading to tumor development and progression. Oncogenes can cause normal cells to become cancerous by altering their normal functions.

Proto-oncogenes are normal genes that promote cell growth and division in a controlled manner. They are essential for the proper functioning of cells and play a critical role in maintaining the balance between cell growth and cell death. However, when mutated or altered, proto-oncogenes can be converted into oncogenes.

There are several ways in which proto-oncogenes can be transformed into oncogenes. These include: 1. Mutation: A change in the DNA sequence of the proto-oncogene can lead to the production of a constitutively active protein, overstimulating cell growth and division. 2. Gene amplification: The number of copies of the proto-oncogene may be increased, leading to overproduction of the protein and uncontrolled cell growth. This can occur through errors in DNA replication or via chromosomal aberrations, such as double-minute chromosomes or homogeneously staining regions. 3. Chromosomal translocation: A piece of the chromosome containing the proto-oncogene may be erroneously swapped with another chromosome, resulting in the production of a chimeric protein with oncogenic properties. This occurs in certain types of leukemia, such as Philadelphia chromosome-positive chronic myeloid leukemia, where the BCR-ABL fusion protein is produced. 4. Insertion of viral DNA: Proto-oncogenes can be activated by the integration of viral DNA into the host cell genome. This can result in the production of a viral oncoprotein or the activation of a cellular oncogene by the viral promoter or enhancer elements. 5. Loss of regulatory elements: The loss of regions in the genome that normally control the expression of proto-oncogenes, such as tumor suppressor genes, can lead to increased expression of proto-oncogenes, uncontrolled cell growth, and the development of cancer. In summary, oncogenes are mutated or altered versions of normal cellular genes called proto-oncogenes. Proto-oncogenes can be converted into oncogenes through several mechanisms, including mutation, gene amplification, chromosomal translocation, insertion of viral DNA, and the loss of regulatory elements. These alterations result in uncontrolled cell growth and division, ultimately leading to the development of cancer.