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Pronunciation: o'o-tid

Definition: The nearly mature oocyte after the first meiotic division has been completed and the second initiated; in most higher mammals, including humans, the second meiotic division is not completed unless fertilization occurs. Thereafter the ootid contains two separate haploid elements, the female and male pronuclei. When the pronuclei fuse, the ootid becomes a zygote.

[G. ootidion, a diminutive egg. See -id (2)]

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© Copyright 2018 Wolters Kluwer. All Rights Reserved. Review date: Sep 19, 2016.