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Oncogenes are mutated genes involved in promoting cell growth, division, and differentiation, which contribute to the development of cancer. Proto-oncogenes, on the other hand, are normal genes that have the potential to become oncogenes if they undergo genetic mutations. In a normal cell, proto-oncogenes regulate cell growth and division, and help in tissue repair and homeostasis.

Oncogenes have altered functions compared to proto-oncogenes, due to the mutations they have undergone. They lead to excessive growth signals being sent to cells, causing uncontrolled cell proliferation and eventually leading to the formation of a tumor. Proto-oncogenes, under normal circumstances, maintain the balance between cell growth, division, and differentiation and ensure cells respond appropriately to signals sent by the body.

The conversion of proto-oncogenes into oncogenes can occur through several mechanisms, which include: a. Gene mutation: When the DNA sequence of a proto-oncogene is altered by mutations, it can create an oncogene capable of promoting uncontrolled cell growth. b. Gene amplification: An increase in the number of copies of a proto-oncogene can lead to its overexpression, causing the cell to receive excessive growth signals, thus transforming the proto-oncogene into an oncogene. c. Chromosomal translocation: The relocation of a proto-oncogene from one part of a chromosome to another can place the gene under the control of a different regulatory element, causing it to be misregulated and converted into an oncogene. d. Viral insertion: A virus may insert its DNA into a host cell, disrupting the function of a proto-oncogene and causing it to become an oncogene, potentially leading to the development of cancer.

In summary, oncogenes and proto-oncogenes are genes that are involved in cellular growth regulation. Proto-oncogenes are normal genes that can become oncogenes through various genetic alterations such as gene mutation, gene amplification, chromosomal translocation, or viral insertion. Oncogenes contribute to uncontrolled cell growth, which is a key factor in the development of cancer.