Human Reproduction
When a primary oocyte completes its first meiotic division at the time of ovulation, which two products are formed?
Select the correct option:
Solution
Secondary oocyte and first polar body
Oogenesis in the human ovary follows an unequal division pattern, detailed in NCERT Class 12, Chapter 3 (Human Reproduction). The diploid primary oocyte completes the first meiotic division, which is reductional, to give a large haploid secondary oocyte and a tiny first polar body. The unequal cytoplasmic division ensures the secondary oocyte retains almost all the cytoplasm and stored nutrients needed for early development. The option of two secondary oocytes is wrong because the division is unequal and yields only one large cell along with a polar body. Ovum and second polar body is incorrect because these form only later, after the second meiotic division, which is completed only if a sperm penetrates the secondary oocyte. Two equal-sized ootids is wrong because oogenesis is characterised by markedly unequal cytoplasmic distribution. A sequence check confirms the answer: meiosis I in the female precedes ovulation and produces a secondary oocyte plus the first polar body, exactly matching the stated stage.
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About This Question
- Subject
- biology
- Chapter
- reproduction
- Topic
- human reproduction
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
Secondary oocyte and first polar body
Oogenesis in the human ovary follows an unequal division pattern, detailed in NCERT Class 12, Chapter 3 (Human Reproduction). The diploid primary oocyte completes the first meiotic division, which is reductional, to give a large haploid secondary oocyte and a tiny first polar body. The unequal cytoplasmic division ensures the secondary oocyte retains almost all the cytoplasm and stored nutrients needed for early development. The option of two secondary oocytes is wrong because the division is unequal and yields only one large cell along with a polar body. Ovum and second polar body is incorrect because these form only later, after the second meiotic division, which is completed only if a sperm penetrates the secondary oocyte. Two equal-sized ootids is wrong because oogenesis is characterised by markedly unequal cytoplasmic distribution. A sequence check confirms the answer: meiosis I in the female precedes ovulation and produces a secondary oocyte plus the first polar body, exactly matching the stated stage.
This medium difficulty biology question is from the chapter reproduction, covering the topic of human reproduction. It appeared in the 2025 exam.
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