Answer: During fertilization, an egg with haploid number of chromosomes unites with a sperm cell with a haploid number of chromosomes to form a zygote with a diploid number of chromosomes.
Explanation: Fertilization is a process in which a sperm cell from a male fuses with an egg from a woman to form a zygote. Sperm cells and eggs are diploid cells and they have half the number of chromosomes as the parent cell. During fertilization the haploid chromosomes from the sperm cells combine with the haploid chromosomes from egg to form a zygote with diploid chromosomes. Diploid cells have the same number of chromosomes as the parent cell. Haploid cells are produced in meiosis while diploid cells are produced in mitosis.