| 释义 |
DictionarySeemonozygotic twinsenzygotic twins
mon·o·zy·got·ic twinstwins resulting from one zygote that at an early stage of development separated into independently growing cell aggregations giving rise to two individuals of the same sex and identical genetic constitution. Synonym(s): enzygotic twins, identical twins, monochorial twins, monovular twins, uniovular twinsmon·o·zy·got·ic twins (mon'ō-zī-got'ik twinz) Twins resulting from a single zygote that at an early stage of development becomes separated into independently growing cell aggregations giving rise to two individuals of the same sex and identical genetic constitution.
Synonym(s): enzygotic twins, identical twins. twin (twin)  TWINS: A. Monozygotic twins with one placenta, one chorion, and two amnions. B. Dizygotic twins with two placentas, two chorions, and two amnions TWINS: A. Monozygotic twins with one placenta, one chorion, and two amnions. B. Dizygotic twins with two placentas, two chorions, and two amnionsOne of two infants born sharing some common anatomical parts. See: illustration; fetus papyraceus; Hellin's lawIncidencePer 1000 live births, incidence rates for American whites are 1:88; for American blacks, 1:70. Generally, the rates are higher in blacks and East Indians and lower in Northern Europeans. Research on TwinsIdentical and fraternal twins provide a unique resource for investigating the origin and natural history of various diseases and discovering the different rates of environmental and hereditary factors in causing physical and mental disorders. Esp. important are studies that follow the course of identical twins separated shortly after birth and who then grew up in different social, economic, educational, and environmental conditions. In other research, the second-born twin was found to be at increased risk for an unfavorable outcome (e.g., need for intubation and resuscitation, lower 5-min Apgar score), even when delivered by cesarean section. biovular twinsDizygotic twins.conjoined twinsTwins that are united. In some cases, the individuals are joined in a small area and are capable of activity, but the extent of union may be so great that survival is impossible. dizygotic twinsTwins from two separate, fertilized ova. Synonym: biovular twins; fraternal twinsenzygotic twinsMonozygotic twins.fraternal twinsDizygotic twins.growth discordant twinsThe unequal growth of twins while in utero. The smaller twin is at greater risk of having congenital anomalies than is the normal birth-weight twin. Synonym: unequal twinsidentical twinsMonozygotic twins.impacted twinsTwins so entwined in utero as to prevent normal delivery.interlocked twinsTwins in which the neck of one becomes interlocked with the head of the other, making vaginal delivery impossible.monozygotic twinsTwins that develop from a single fertilized ovum. Monozygotic twins have the same genetic makeup and, consequently, are of the same gender and strikingly resemble each other physically, physiologically, and mentally. They develop within a common chorionic sac and have a common placenta. Each usually develops its own amnion and umbilical cord. Such twins may result from development of two inner cell masses within a blastocyst, development of two embryonic axes on a single blastoderm, or the division of a single embryonic axis into two centers. Synonym: enzygotic twins; identical twins; true twins; uniovular twinsparasitic twinThe smaller of a pair of conjoined twins, when there is a marked disparity in size.Siamese twinsA culturally insensitive term for conjoined twins. See: conjoined twintrue twinsMonozygotic twins.unequal twinsGrowth discordant twins.uniovular twinsMonozygotic twins.vanishing twinFetal resorption in multiple gestation. See: gestation, multipleThesaurusSeetwin |