AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
When two germ-cells (sperm and egg) fuse during fertilisation, the resulting zygote must have the normal chromosome number. If each germ-cell had the full number of chromosomes, the zygote would have double the normal number, which would be non-viable. Therefore, germ-cells contain only half the chromosomes so that their fusion restores the correct chromosome number in the offspring.
Source: Chapter 7, Reproduction
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The examiner wants you to show you understand the logic of halving: fertilisation = fusion of two cells, so each must contribute exactly half. Key terms to use: germ-cells, fertilisation, zygote, and chromosome number. Two marks = two linked points — (1) fusion doubles the count, (2) so halving beforehand keeps it normal. Avoid vague statements like "so reproduction works."