Mutation is nothing but change in the building block of genome that is DNA. Mutations can be caused by radiation, mutagens (chemical substances), or may be at time by malfunctioning of some enzymes during meiosis or DNA replication.

Mutation in a single base can also affect cells function by altering the structure of a protein so that it no longer able to work the way it should work in a cell. Mutations may also stop some protein production itself. All this leads some form of disorder or disease in Humans or living being.

The mutations in the Oncogene and Tumor suppressor gene may lead to the formation of tumor or cancer.


Most of the oncogenes are formed by the mutations which are occurred in Proto-oncogenes. Proto-oncogenes are normal gene which regulates the cell cycle of a healthy cell. When mutations occur in Proto-oncogenes the cell divides continuously and may cause tumor or cancer.

Inherited form of Oncogene mutations:

A small number of cancers can be inherited due to the transmission of muted Proto-oncogene from the parents. This mutated form of Proto-oncogene activates the oncogene and may cause cancer in off-springs. For example inherited mutations in the gene called as MET causes papillary renal cancer. Inherited mutation in the gene KIT causes hereditary gastrointestinal stromal tumor (GIST). Inherited mutations in the gene called as RET causes multiple endocrine neoplasia 2 which in turn leads to thyroid cancer known as medullary cancer of the thyroid. They may also develop other cancers like pheochromocytoma and nerve tumors

Acquired form of Oncogene mutations:

In a lot of cases oncoge mutations are acquired but not inherited. Acquired oncogene mutations may occur by chromosome rearrangements, gene duplication, or may be by mutation. For example, one form of chromosome rearrangement leads to the formation of an oncogene called as BCR-ABL. This change in the gene leads to the disease known as chronic myeloid leukemia (CML). Acquired mutation which activates the oncogene known as KIT causes most cases of gastrointestinal stromal tumor (GIST).


Tumor suppressor genes are normal genes which controls the activity of a cell. Such as cell division, apoptosis and also will repair DNA damages occurred during DNA replication. When mutations occur in tumor suppressor gene cells can divide continuously and may lead to the formation of a cancer. Some of the examples for tumor suppressor gene are p53, BRCA1, BRCA2, APC, and RB1.

Inherited form of Tumor Suppressor Gene Mutations:

In some cases mutated form of tumor suppressor gene run in families. These inherited mutations cause some types of cancer. For example mutation in the gene called as APC leads to familial adenomatous polyposis (FAP), in this the patient develops hundreds of colon polyps. Many times at least one in hundred polyps becomes cancerous leading to a condition known as colon cancer.

Acquired form of Tumor Suppressor Gene Mutations:

In most cases tumor suppressor gene mutations are acquired but not inherited. For example p53 tumor suppressor gene mutation has been found in a number of cancers, like lung, colorectal, and breast cancer. Protein p53 involved in the pathway of programmed cell death and also repairs damaged DNA. When mutation occurs in p53 gene it produces abnormal p53 protein leading to continuous division of cells with abnormal or damaged DNA. This leads to the formation of tumor or cancer in humans.

Major difference between oncogenes and tumor suppressor genes is that oncogenes are produced when proto-oncogenes are activated, but tumor suppressor genes cause cancer when they are inactivated

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