Kariogamia

Kariogamia is a biological term referring to the fusion of two nuclei. This process is a critical stage in sexual reproduction, occurring after the fusion of gametes, a process known as plasmogamy. In many eukaryotic organisms, including fungi and some protists, plasmogamy results in a transient dikaryotic stage where two distinct haploid nuclei coexist within a single cell. Kariogamia then marks the actual union of these two nuclei, forming a single diploid nucleus. This diploid nucleus contains a complete set of chromosomes, with contributions from both parental gametes. Following kariogamia, the cell is typically considered a zygote. This diploid nucleus then undergoes meiosis to produce haploid cells, which can develop into new individuals or gametes, thus completing the sexual reproductive cycle. The precise timing and mechanism of kariogamia can vary significantly between different species. It is a fundamental step that restores the diploid chromosome number characteristic of the somatic cells of many sexually reproducing organisms.