Question at position 9 Proto-oncogenes are required for normal cell division.tumor suppressors.cancer causing in normal cells.mutations in oncogenes.tumor regulators.Clear my selection

Question

Question at position 9  Proto-oncogenes are required for normal cell division.tumor suppressors.cancer causing in normal cells.mutations in oncogenes.tumor regulators.Clear my selection

BlackTom AI · Accepted Answer

Proto-oncogenes encode proteins that promote and regulate normal cell growth and division, so the correct option is "required for normal cell division."

1) Relevant knowledge points and concepts
- Proto-oncogenes: normal cellular genes whose protein products (growth factors, receptors, intracellular signaling molecules, transcription factors) stimulate cell proliferation and survival.
- Oncogenes: mutated or abnormally expressed proto-oncogenes that drive uncontrolled cell division and can contribute to cancer.
- Tumor suppressor genes: a different class of genes that normally inhibit cell division or promote apoptosis; loss-of-function mutations here also promote cancer.

2) Step-by-step reasoning
- In their normal (wild-type) state, proto-oncogenes produce proteins essential for regulated progression through the cell cycle and appropriate responses to growth signals.
- If a proto-oncogene acquires a gain-of-function mutation (e.g., point mutation, gene amplification, chromosomal translocation), it becomes an oncogene and can cause excessive proliferative signaling.
- Therefore, by definition proto-oncogenes are required for normal cell division; only when altered do they contribute to tumorigenesis.

3) Calculations / intermediate steps
- No numerical calculations are required. The conceptual transformation steps are: proto-oncogene (normal function) → mutation/amplification/translocation → oncogene (constitutive activation) → potential cancerous growth.

4) Why the correct answer is correct
- The phrase "required for normal cell division" matches the established definition: proto-oncogenes encode proteins that actively promote and regulate cell proliferation under normal conditions. Their normal function is necessary for controlled cell division.

5) Why the other options are incorrect
- "tumor suppressors.": Tumor suppressor genes are distinct and act to inhibit division; proto-oncogenes are not tumor suppressors.
- "cancer causing in normal cells.": Misleading—proto-oncogenes in their normal form do not cause cancer; mutated forms (oncogenes) can.
- "mutations in oncogenes.": Incorrect direction—the concept is proto-oncogenes can be mutated to form oncogenes, not that proto-oncogenes are mutations in oncogenes.
- "tumor regulators.": Vague and non-specific; while proto-oncogenes influence growth, the precise definition is that they are required for normal cell division.

6) Conclusion
This reasoning confirms the correct answer is: required for normal cell division.

Question at position 9 Proto-oncogenes are required for normal cell division.tumor suppressors.cancer causing in normal cells.mutations in oncogenes.tumor regulators.Clear my selection单项选择题

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