quadruplet

biology

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multiple birth

  • identical and fraternal twins
    In multiple birth: Other multiple births

    Similarly, quadruplets may originate from one up to four zygotes, and quintuplets may derive from one to five zygotes. After being carefully studied, the Canadian Dionne quintuplets (born in 1934) were shown to be a one-zygote set.

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twin, either of two young who are simultaneously born from one mother. Twinning, common in many animals, is of two biological kinds: the one-egg (monozygotic), or identical, type and the two-egg (dizygotic), or fraternal, type. The latter type is more usual and can be thought of simply as a litter of two. In humans, psychological studies of sets of identical twins, since they are genetically identical, have provided much otherwise unobtainable information on the relative effects of genetic endowment and environment. See also multiple birth.

This article was most recently revised and updated by Amy Tikkanen.
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