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Cancerous cells have two major genes that contributes in transformation of normal cell into a cancerous one. Oncogenes and tumor suppressor genes. They both differ from each other in many ways like how they are inherited or how they function. Oncogenes helps the cell to grow but when it gets mutated it becomes a cancer causing oncogene. Tumor suppressor genes are found normally and their function is to regulate the division of the cell, mutation in a tumor suppressor gene cause uncontrolled division of cells.
What is Oncogene?
Proto-oncogene, genes that codes for different proteins and helps in regulation of cell division. When mutation (change in DNA sequence) occurs, it gives rise to oncogene which interferes with the regulation of normal cell division. Proto-oncogene must respond to two signals that is when proto-oncogenes produces the proteins which signals the cell division to start and other is proto-oncogene must respond to tumor suppressor gene which signals the cell division to stop. When a proto-oncogene gets mutated, it becomes abnormal and called as oncogene. An oncogene have no response to stop signal produced by tumor suppressor gene. So, the cell grows out of control which in turn leads to cancer. Even if the mutation of a single allele of the proto-oncogene occurs, it is sufficient for an activity of an oncogene. Some times this single mutation is enough for the cancer to behave aggressively, if two oncogene allele are present then it results in fast growing tumor. So oncogene allele will result in cancer even if the partner allele is proto-oncogene (normal one). There are basically three methods of activation which results a proto-oncogene to become an oncogene: mutation within a proto-oncogene, increase in protein concentration and chromosomal abnormality. Oncogenes cannot be inherited.
What is Tumor Suppressor Gene?
Tumor suppressor genes are normally found in our cells. They also functions in regulation of cell division by slowing down the division, coupling the cell cycle to DNA damage, repairing the DNA or mark the cells when to die. Tumor suppressor gene codes for a protein which act as “stop” signal for the division of the cell. The protein must be normal to stop the cell division. If the tumor suppressor gene gets mutated it results in abnormal protein which causes uncontrolled cell division. Tumor suppressor gene is different from oncogene, an oncogene results from the activation of proto-oncogene while tumor suppressor gene causes cancer when they are inactivated. A single mutant allele of tumor suppressor gene is not sufficient to cause cancer because the other normal allele will produces the protein that stops the cell division. So two mutant tumor suppressor genes will result in cancer because there is no other normal gene present to signal the cell division to stop. Tumor suppressor gene can be inherited.
- Oncogene results from the activation of the proto-oncogene while tumor suppressor gene results in cancer when they are inactivated.
- Mutation in single allele is enough for oncogene to cause cancer while for tumor suppressor gene, mutation should occur in two alleles to cause cancer.
- Mutation in oncogene allele occurs in somatic cells therefore they are not inherited, while tumor suppressor gene, mutation can be occur in germ cell or somatic cell and therefore can be inherited.
- Gain of function mutation is the reason of conversion of a proto-oncogene to oncogene while loss of function mutation is the reason for tumor suppressor gene improper functioning.