Assertion (A): Mitochondria and chloroplasts are considered semi-autonomous organelles. Reason (R): They possess their own DNA and ribosomes, and can synthesize some of their own proteins. MCQ with Answer and Explanation

Assertion (A): Mitochondria and chloroplasts are considered semi-autonomous organelles. Reason (R): They possess their own DNA and ribosomes, and can synthesize some of their own proteins.
A. A is true, but R is false.
B. Both A and R are true, and R is the correct explanation of A.
C. Both A and R are true, but R is not the correct explanation of A.
D. A is false, but R is true.
Answer: Option B
Solution (By JKExamLibrary)
Mitochondria and chloroplasts contain circular DNA and 70S ribosomes, enabling them to transcribe and translate some proteins independently, though they rely on nuclear genes for most proteins. This partial autonomy supports the endosymbiotic origin hypothesis. The presence of their own genetic material and protein synthesis machinery qualifies them as semi-autonomous. Thus, both assertion and reason are correct, and the reason correctly explains the assertion.

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Practice More Biology Questions

Question #1
Consider the following statements about DNA replication:
1. It is semiconservative.
2. It requires DNA polymerase.
3. It occurs in the cytoplasm of eukaryotic cells.
Which of the above is/are correct?
A. 2 and 3 only
B. 1, 2, and 3
C. 1 and 2 only
D. 1 and 3 only

Correct Answer: Option C


Explanation:
DNA replication is semiconservative and uses DNA polymerase. In eukaryotes, it occurs in the nucleus, not cytoplasm. So statement 3 is incorrect.

This question belongs to: Science Biology
Question #2
Consider statements about evolution: 1. The theory of use and disuse was given by Lamarck. 2. The theory of natural selection was given by Darwin. 3. The theory of mutation was given by Hugo de Vries. Which are correct?
A. 1, 2 and 3
B. 1 and 2 only
C. 1 and 3 only
D. 2 and 3 only

Correct Answer: Option A


Explanation:
Jean-Baptiste Lamarck proposed the theory of inheritance of acquired characters, based on the use and disuse of organs. Charles Darwin proposed the theory of evolution by natural selection, emphasizing survival of the fittest. Hugo de Vries, a Dutch botanist, proposed the mutation theory of evolution after working on evening primrose, stating that evolution occurs via sudden, large mutations (saltations). All statements are correct.

This question belongs to: Science Biology
Question #3
Consider statements about scientists: 1. Edward Jenner is the father of immunology. 2. Alexander Fleming discovered penicillin. 3. Louis Pasteur discovered the structure of DNA. Which are correct?
A. 2 and 3 only
B. 1, 2 and 3
C. 1 and 3 only
D. 1 and 2 only

Correct Answer: Option D


Explanation:
Edward Jenner is considered the father of immunology for pioneering the concept of vaccination by developing the smallpox vaccine. Alexander Fleming discovered the first antibiotic, penicillin, from the fungus Penicillium notatum in 1928. Louis Pasteur made monumental contributions to microbiology and vaccination, but the structure of DNA was discovered by James Watson and Francis Crick in 1953. Thus, statements 1 and 2 are correct.

This question belongs to: Science Biology