After fertilization, the zygote is diploid.

• A. Haploid
• B. Diploid
• C. Triploid
• D. Polyploid

Answer: (B)

The zygote is diploid because fertilization brings together two complete haploid sets of chromosomes, one from each parent. Each gamete has a single set (n), so when they fuse, the zygote contains two sets (2n). In humans, that totals 46 chromosomes. This diploid state is what the organism uses as it begins mitotic divisions to form all somatic cells, while meiosis in the gonads produces haploid gametes for the next generation. If an abnormal fertilization event occurred—such as multiple sperm entering the egg or a genome doubling—the zygote could become triploid or polyploid, but under normal fertilization, the zygote is diploid.