1. Plasmogamy : The union of protoplasm of two cells or gametes is called plasmogamy. The two gametes approach each other and their protoplasm fuses.
2. Karyogamy: Plasmogamy results in the cell having two haploid nuclei. This condition is called dikaryon. The nucleus is two heterokaryons (+, -) in nature. The two nuclei move closer together and fuse. The union of nuclei is called karyogamy. Karyogamy results in the formation of a diploid nucleus.
3. Meiosis: The diploid zygote divides by the process of meiosis to form a new zygote.