MeSH

Two individuals derived from two FETUSES that were fertilized at or about the same time, developed in the UTERUS simultaneously, and born to the same mother. Twins are either monozygotic (TWINS, MONOZYGOTIC) or dizygotic (TWINS, DIZYGOTIC).

Two off-spring from the same PREGNANCY. They are from a single fertilized OVUM that split into two EMBRYOS. Such twins are usually genetically identical and of the same sex.

Year introduced: 1991(1975)

Two offspring from the same PREGNANCY. They are from two OVA, fertilized at about the same time by two SPERMATOZOA. Such twins are genetically distinct and can be of different sexes.

Year introduced: 1991(1975)

MONOZYGOTIC TWINS who are joined in utero. They may be well developed and share only a superficial connection, often in the frontal, transverse or sagittal body plane, or they may share a partial duplication of a body structure. Alternatively, there may be a small and incompletely developed twin conjoined to a larger, more fully developed twin.

Year introduced: 1966

Disorders affecting TWINS, one or both, at any age.

amino acid sequence given in first source; aar(1) phenotype caused by a defect in PR55 function; a regulatory subunit of Drosophila protein phosphatase 2A; RefSeq NM_057532

Date introduced: March 25, 1993