O Levels Biology (5090)•5090/11/O/N/21
Explanation
Correct statements on chromosomes Steps:
- Statement 1 is correct: Chromosomes contain long DNA molecules packaged with proteins.
- Statement 2 is correct: Genes are specific DNA sequences located on chromosomes.
- Statement 3 is incorrect: Meiosis halves the chromosome number for gametes; mitosis maintains it during somatic cell division.
- Statement 4 is correct: Normal human somatic cells have 46 chromosomes (23 pairs).
Why A is correct:
- A selects exactly the true statements (1, 2, and 4), aligning with basic genetics definitions.
Why the others are wrong:
- B includes false statement 3 about meiosis.
- C omits true statements 1 and 4 while including false 3.
- D omits true statements 1 and 2 while including false 3.
Final answer: A
Topic: Nuclear division
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