At fertilization
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Correct Answer: Option C
Explanation:
At fertilization, the male gamete (sperm) and the female gamete (egg or ovum) each contribute a haploid nucleus (with half the number of chromosomes). These two nuclei fuse to form a diploid zygote nucleus — this fusion is the key event in fertilization.
Quick clarifications on the other options:
A: Chromosomes don't individually join like that — it's the entire nuclei that fuse.
B: Genes are just segments of DNA; fertilization is about nuclei combining, not individual genes.
D: Sounds close, but it's vague. It's the nuclei (each containing a set of chromosomes) that fuse.
E: Again, sounds close, but not precise — it's not just the cells fusing, it's the nuclear fusion that defines fertilization.
At fertilization, the male gamete (sperm) and the female gamete (egg or ovum) each contribute a haploid nucleus (with half the number of chromosomes). These two nuclei fuse to form a diploid zygote nucleus — this fusion is the key event in fertilization.
Quick clarifications on the other options:
A: Chromosomes don't individually join like that — it's the entire nuclei that fuse.
B: Genes are just segments of DNA; fertilization is about nuclei combining, not individual genes.
D: Sounds close, but it's vague. It's the nuclei (each containing a set of chromosomes) that fuse.
E: Again, sounds close, but not precise — it's not just the cells fusing, it's the nuclear fusion that defines fertilization.