identical twins


Also found in: Dictionary, Thesaurus, Legal, Encyclopedia, Wikipedia.

mon·o·zy·got·ic twins

twins 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.

identical twins

identical twins

Monozygotic twins Twins resulting from the division of a single fertilized egg, which usually share a common chorion and placenta, although usually each may have a separate amnion. Cf Fraternal twins.

mon·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)
Enlarge picture
TWINS: A. Monozygotic twins with one placenta, one chorion, and two amnions. B. Dizygotic twins with two placentas, two chorions, and two amnions
Enlarge picture
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

Incidence

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

identical twins

Twins derived from the same egg (ovum) which, after the first division, has separated into two individuals. Identical twins thus have the same genetics.

identical twins

see MONOZYGOTIC TWINS.

identical twins

monozygotic twins.
References in periodicals archive ?
Still, other work has shown that identical twins can have different gene mutations, but this study didn't determine how often they occur.
Delighted North mum Charlotte Kelly is seeing double again - after delivering her second set of identical twin girls.
However, one study published in the Depression and Anxiety journal, found identical twins had much closer scores on measures of perfectionism and anxiety than non-identical twins.
And now a local paper has reported that a set of identical twin boys suffered the same fate in 1973.
For example, Manel Esteller of the Spanish National Cancer Center in Madrid and his colleagues reported in the July 26, 2005 Proceedings of the National Academy of Sciences that identical twins who start out with near-identical methylation patterns grow apart epigenetically as they age (SN: 7/9/05, p.
If I saw them in the paper I would have to vote for both or neither - it's just so obvious they are identical twins.
PHOTO Identical twins Mark, left, and Michael Polish star in the quirky little love story ``Twin Falls Idaho.
Like most identical twins, the Hensel girls look very much alike.
By comparing the disease rates between identical twins and fraternal twins, scientists can dissect the relative contributions of genes and environment to disease development.
Because identical twins share virtually 100 percent of their genes, this is strong evidence for the role of genetics in autism," Losh said.
A recent US study found that minute chemical changes occur to DNA as people age, and these may enable scientists to distinguish identical twins genetically.
Although identical twins have identical DNA, they often harbor clear-cut differences: slight variations in appearance or stark distinctions in disease susceptibility, for example.