begin the gastrulation stage of embryonic development. The human zygote has been genetically edited in experiments designed to cure inherited diseases. Fungi In fungi, the sexual fusion of haploid cells is called karyogamy. The result of karyogamy is the formation of a diploid cell called the zygote or zygospore. This cell may then enter meiosis or mitosis depending on the life cycle of the species. Plants In plants, the zygote may be polyploid if fertilization occurs between meiotically unreduced gametes. In land plants, the zygote is formed within a chamber called the archegonium. In seedless plants, the archegonium is usually flask-shaped, with a long hollow neck through which the sperm cell enters. As the zygote divides and grows, it does so inside the archegonium. Reprogramming to totipotency The formation of a totipotent zygote with the potential to produce a whole organism depends on epigenetic reprogramming. DNA demethylation of the paternal genome in the zygote appears to be an important part of epigenetic reprogramming. In the paternal genome of the mouse, demethylation of DNA, particularly at sites of methylated cytosines, is likely a key process in establishing totipotency. Demethylation involves the processes of base excision repair and possibly other DNA- repair- based mechanisms. In other species A Chlamydomonas zygote contains chloroplast DNA (cpDNA) from both parents; such cells are generally rare, since normally cpDNA is inherited uniparentally from the mt+ mating type parent. These rare biparental zygotes allowed mapping of chloroplast genes by recombination. In protozoa In the amoeba, reproduction occurs by cell division of the parent cell: first the nucleus of the parent divides into two and then the cell membrane also cleaves, becoming two "daughter" Amoebae. See also Breastfeeding and fertility Fertilization Proembryo References Developmental biology Human pregnancy