Why must each gamete (reproductive cell) carry only ONE copy of each gene, even though all other body cells carry two copies? What would happen to the chromosome number in offspring if gametes were not formed this way?
Generated by claude-sonnet-4-6 · 2026-06-26 01:04 · grounding rag
Model Answer
Body cells carry two copies of each gene (one from each parent). When two gametes fuse during fertilisation, the offspring must receive the correct total — two copies. To ensure this, gametes are formed by meiosis, carrying only one copy (half the chromosomes).
If gametes were not formed this way, each fertilisation would double the chromosome number in every generation, disrupting the cell's genetic control and making normal development impossible.
Source: Chapter 7, Section 7.3.1 — Why the Sexual Mode of Reproduction?
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Explanation
- The key idea is meiosis halving the chromosome number so fertilisation restores it.
- Examiners expect two clear points: (1) why gametes have half — so fusion gives the correct number; (2) consequence if they didn't — chromosome number doubles each generation.
- Quote or paraphrase the textbook phrase: "re-establishment of the number of chromosomes and DNA content in the new generation."
- Avoid over-explaining; two focused sentences covering both marks is sufficient.