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Question
Statement I : Proto oncogenes are present in normal cells.
Statement II : Proto oncogenes may cause malignant tumors in animals, if activated.
Which of the above statement(s) are correct?
Statement I : Proto oncogenes are present in normal cells.
Statement II : Proto oncogenes may cause malignant tumors in animals, if activated.
Which of the above statement(s) are correct?
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Solution
The correct option is C Both Statement I and II
Genetic material that has the ability to induce cancer is an oncogene whereas proto oncogene is the sequence of DNA that has been altered or mutated.
The proto oncogene acts as a positive growth regulator, and is involved in promoting the differentiation and proliferation of normal cells.
Mutations can cause hyperactivity in proto oncogene and can be genetically dominant which facilitates the formation of tumors even in the presence of a normal gene on the homologous chromosome. The mutant, cancer-promoting forms of genes are referred to as oncogenes and their normal versions are referred to as proto oncogenes.
There are some viruses that can induce cancer by activating the proto oncogenes. Examples include oncogenic viruses like Human papillomavirus, Epstein-Barr virus, and hepatitis B virus. Even when these viruses infect cultured cells, they cause cancerous transformations to the cells.
Figure : Transformation of a normal cell to cancer cell
As shown in the image, retroviral infection can convert a proto oncogene into an oncogene. For example, a retrovirus produces tumors within weeks of infection. It incorporates genetic material (proto oncogene) from a host cell into its own genome upon infection and onverts it into a viral oncogene.
This newly formed viral oncogene infects another cell, that time an enzyme called reverse transcriptase copies the single stranded genetic material into a double stranded DNA, which gets integrated into the cellular genome.
A slowly transforming retrovirus requires months to elicit tumor growth, and does not disrupt normal cellular function. The insertion of a viral oncogene, integrated into the genome of the host cell next to or within a proto oncogene, converts proto oncogene into an oncogene. This leads to uncontrolled cell growth, resulting in the formation of a cancerous tumor.
Genetic material that has the ability to induce cancer is an oncogene whereas proto oncogene is the sequence of DNA that has been altered or mutated.
The proto oncogene acts as a positive growth regulator, and is involved in promoting the differentiation and proliferation of normal cells.
Mutations can cause hyperactivity in proto oncogene and can be genetically dominant which facilitates the formation of tumors even in the presence of a normal gene on the homologous chromosome. The mutant, cancer-promoting forms of genes are referred to as oncogenes and their normal versions are referred to as proto oncogenes.
There are some viruses that can induce cancer by activating the proto oncogenes. Examples include oncogenic viruses like Human papillomavirus, Epstein-Barr virus, and hepatitis B virus. Even when these viruses infect cultured cells, they cause cancerous transformations to the cells.
Figure : Transformation of a normal cell to cancer cellAs shown in the image, retroviral infection can convert a proto oncogene into an oncogene. For example, a retrovirus produces tumors within weeks of infection. It incorporates genetic material (proto oncogene) from a host cell into its own genome upon infection and onverts it into a viral oncogene.
This newly formed viral oncogene infects another cell, that time an enzyme called reverse transcriptase copies the single stranded genetic material into a double stranded DNA, which gets integrated into the cellular genome.
A slowly transforming retrovirus requires months to elicit tumor growth, and does not disrupt normal cellular function. The insertion of a viral oncogene, integrated into the genome of the host cell next to or within a proto oncogene, converts proto oncogene into an oncogene. This leads to uncontrolled cell growth, resulting in the formation of a cancerous tumor.
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