fraternal twins

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di·zy·got·ic twins

twins derived from two zygotes.
Farlex Partner Medical Dictionary © Farlex 2012

fraternal twins

Dizygotic twins Twins resulting from 2 separate fertilized eggs liberated simultaneously from the ovaries that develop in separate or partially fused chorionic sacs; 70-80% of twins are dizygotic. Cf Identical twins.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

di·zy·got·ic twins

(dī-zī-got'ik twinz)
Twins derived from two zygotes.
Synonym(s): fraternal twins, heterologous twins.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


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TWINS: A. Monozygotic twins with one placenta, one chorion, and two amnions. B. Dizygotic twins with two placentas, two chorions, and two amnions
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TWINS: A. Monozygotic twins with one placenta, one chorion, and two amnions. B. Dizygotic twins with two placentas, two chorions, and two amnions
One of two infants born sharing some common anatomical parts. See: illustration; fetus papyraceus; Hellin's law


Per 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 Twins

Identical 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 twins

Dizygotic twins.

conjoined twins

Twins 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 twins

Twins from two separate, fertilized ova. Synonym: biovular twins; fraternal twins

enzygotic twins

Monozygotic twins.

fraternal twins

Dizygotic twins.

growth discordant twins

The 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 twins

identical twins

Monozygotic twins.

impacted twins

Twins so entwined in utero as to prevent normal delivery.

interlocked twins

Twins in which the neck of one becomes interlocked with the head of the other, making vaginal delivery impossible.

monozygotic twins

Twins 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 twins

parasitic twin

The smaller of a pair of conjoined twins, when there is a marked disparity in size.

Siamese twins

A culturally insensitive term for conjoined twins.
See: conjoined twin

true twins

Monozygotic twins.

unequal twins

Growth discordant twins.

uniovular twins

Monozygotic twins.

vanishing twin

Fetal resorption in multiple gestation.
See: gestation, multiple
Medical Dictionary, © 2009 Farlex and Partners

fraternal twins

Non-identical twins produced by the simultaneous fertilization of two different eggs by different sperms (dizygotic twins). In spite of the etymology, fraternal twins need not be male or even of the same sex.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

fraternal twins

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
References in periodicals archive ?
With her fraternal twin, Joyce, Pat was a guiding light in the Yngling class, which made its entrance to the Olympic Games in 2004.
This study includes identical twins, fraternal twins and a third group called virtual twins.
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That rate was only 20 percent in fraternal twins. In 1993 Dean Hamer discovered that homosexual brothers shared a specific region of their X chromosome, labeled Xq28, at a higher rate than other homosexuals shared with their heterosexual brothers.
Ford was one of fraternal twins born to the Very Reverend Lionel Ford, headmaster at Harrow and then Dean of York.
Author Nancy Segal is Professor of Psychology of the Twin Studies center at CSU Fullerton: her professional career has been devoted to the study of identical and fraternal twins, and INDIVISIBLE BY TWO: LIVES OF EXTRAORDINARY TWINS reflects this long history, following up on her ENTWINED LIVES to reveal the lives of 10 sets of twins, one set of triplets and a set of quads.
"It was when we went for the 12-week scan that they told us they were fraternal twins - and we weredelighted." There was no sign that anything was wrong until Lena went for another scan on May 17 at Birmingham's Heartlands Hospital.
Genetically identical twins raised in the same environment are three times more likely to both have major depressive disorder than are fraternal twins, who have only about half their genes in common.
Researchers find that 52% of identical twin brothers of gay men were also gay, compared with 22% of fraternal twins and just 11% of adoptive brothers.
They finally decided that they are fraternal twins who were developed in different mothers.
And it should be mentioned that just as the aforementioned vehicles have fraternal twins, so too does the Aveo: the Kalos platform, which has been available in Asia and Europe.