For other meanings see Zygote (disambiguation).

A zygote (from Greek ??????? zug?tos "joined" or "yoked", from ?????? zugoun "to join" or "to yoke")^[1] is a cell that is the result of fertilization. That is, two haploid cells—usually an ovum from a female and a sperm cell from a male—merge into a single diploid cell called the zygote (or zygocyte).

Variations in different species

Animal zygotes undergo mitotic cell divisions to become a blastocyst then an embryo.^[2] A zygote has all of the DNA required to grow into a fetus for birth.^[2] Other organisms may undergo meiotic cell division at this time (for more information refer to biological life cycles).

In mammals, fusion of the sperm with the ovacyte occurs in the fallopian tube and the resulting diploid zygote becomes embedded in the uterine wall.^[2] In humans, the blastocyst often reaches the uterus in five days. On the sixth day, the blastocyst implants itself into the uterine wall.^[2]

Twins

Twins and multiple births can be monozygotic (identical) or dizygotic (fraternal), meaning they arise from one or several (strictly, two) fertilization events. Polyspermic zygotes in mice have been manipulated so as to remove one of the two male pronuclei and made to survive birth.^[3]

In other species

A biparental zygote is a Chlamydomonas (a kind of algae) zygote that contains chloroplast DNA (cpDNA) from both parents.

References

See also

• Sexual reproduction
• Zygote intrafallopian transfer
• Twin Zygosity

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