"Stability of DNA in a species is ensured during sexual reproduction." Justify the statement.
"Stability of DNA in a species is ensured during sexual reproduction." Justify the statement.
The stability of DNA in a species is ensured during sexual reproduction through the following mechanism:
- Meiosis (Reduction Division): Special lineages of cells in the reproductive organs undergo a specific type of cell division called meiosis. This process halves the number of chromosomes and the amount of DNA () in the germ-cells (gametes) compared to the non-reproductive body cells ().
- Fertilisation (Restoration): When the male gamete () and female gamete () fuse during fertilisation, they form a zygote. This fusion re-establishes the original diploid number of chromosomes and the original DNA content () in the new generation, maintaining genomic stability across generations.
Marking Scheme
- 1Explanation of meiosis/reduction division halving the chromosome number/DNA content in gametes: 1 Mark
- 2Explanation of fertilisation restoring the original diploid chromosome number/DNA content in the zygote: 1 Mark
Hint
Think about how meiosis halves the chromosome number in gametes and how fertilisation restores it.
Quick Oral Answer
Stability of DNA is maintained because gametes are formed by meiosis, which halves the chromosome number. When these gametes fuse during fertilisation, the original diploid chromosome number is restored in the zygote.
Analysis & Explanation
If sexual reproduction simply combined the DNA of two normal body cells (), the offspring would end up with twice the amount of DNA (). This would severely disrupt the control of the cellular apparatus. To prevent this, multicellular organisms have evolved specialized germ-cells (gametes) that contain only half the amount of DNA () due to meiosis. When these haploid gametes fuse, the original diploid chromosome number () is restored, ensuring species-specific DNA stability.
Common Mistakes
- 1Forgetting to mention the term 'meiosis' or 'reduction division'.
- 2Failing to explain that fertilisation restores the original chromosome number, only mentioning that gametes have half the DNA.
Interesting Facts
Without meiosis, the chromosome number would double with every single generation! Within just 10 generations, a human cell would contain over 47,000 chromosomes, which is biologically impossible to sustain.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2024?
This question carries 2 marks in the CBSE Class 10 Science 2024 examination.
Which chapter does this question come from in Science?
This question is from the chapter "How do Organisms Reproduce?" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Why the Sexual Mode of Reproduction?" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2024 paper?
This is a Very Short Answer question from Section B in the CBSE Class 10 Science 2024 paper.