In human body, the cell growth and differentiation are highly controlled and regulated, but in cancer cells
- A.there is breakdown of these regulatory mechanisms leading to formation of benign and malignant tumors
- B.controlled cell division and over-production of genetic material occur
- C.RNA is mutated and produced in less amount
- D.DNA is mutated and produced in less amount
Correct answer
Explanation
The correct answer is A, there is breakdown of these regulatory mechanisms leading to formation of benign and malignant tumors. Cancer is uncontrolled cell division that follows the loss of the checks that normally govern growth.
Normal cells divide only when signalled and stop when they touch neighbouring cells, a property called contact inhibition. Mutations in genes that control the cell cycle, such as proto-oncogenes and tumour suppressor genes, remove these brakes. The cells then multiply without limit and form a mass called a tumour. A benign tumour stays at its site, while a malignant tumour invades nearby tissue and spreads through blood and lymph to other organs, a process called metastasis. Carcinogens such as tobacco smoke, ionising radiation and some viruses cause these mutations.
B is wrong: cancer cell division is uncontrolled, not controlled.
C is wrong: cancer arises from changes in DNA, and RNA is not produced in less amount.
D is wrong: DNA is mutated, but cancer cells copy it constantly as they divide, so it is not produced in less amount.
Exam tip: benign = stays put; malignant = spreads (metastasis); loss of contact inhibition is the hallmark of cancer cells.
Practice Questions
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- D.motile male gametes
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- A.One
- B.Two
- C.Three
- D.Four
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- A.10⁻⁷ cm
- B.10⁻⁶ cm
- C.10⁻⁴ cm
- D.10⁻³ cm
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- A.CₙH₂ₙ₊₂
- B.CₙH₂ₙ₋₂
- C.CₙH₂ₙ₊₁
- D.CₙH₂ₙ₋₁
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- A.Cholera
- B.Malaria
- C.Smallpox
- D.Elephantiasis
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