Twin Registry
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A twin registry is a
database In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and a ...
of information about both
identical twins Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of Twin Last Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two e ...
and
fraternal twins Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of Twin Last Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two e ...
, which is often maintained by an academic institution, such as a university, or by other research institutions.


Investigative use

The use of twins can improve the statistical power of a genetic study by reducing the amount of genetic and/or environmental variability.NIEHS Twin Registry
accessed 2013-06-14. (Some of the text in this article is a close paraphrase of the material on this website maintained by the U.S. Federal Government, and which is a document in the public domain.)
"Identical twins" (
monozygotic Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of Twin Last Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two e ...
(MZ) twins) share virtually all their
genes In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
with each other, and "fraternal twins" (
dizygotic Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of Twin Last Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two e ...
(DZ) twins), on average, share about 50% of their genes with each other (about the same amount of sharing as non-twin siblings). Both types of twin pairs in twin registries almost always share similar
prenatal Prenatal development () involves the embryonic development, development of the embryo and of the fetus during a viviparity, viviparous animal's gestation. Prenatal development starts with fertilization, in the germinal stage of embryonic develop ...
and early childhood environments as well. By determining what are called " concordance" rates for a disease or trait among identical and fraternal twin pairs, researchers can estimate whether contributing factors for that disease or trait are more likely to be hereditary, environmental, or some combination of these. A concordance rate is a statistical measure of probability - if one twin has a specific trait or disease, what is the probability that the other twin has (or will develop) that same trait or disease. In addition, with
structural equation modeling Structural equation modeling (SEM) is a diverse set of methods used by scientists for both observational and experimental research. SEM is used mostly in the social and behavioral science fields, but it is also used in epidemiology, business, ...
and multivariate analyses of twin data, researchers can offer estimates of the extent to which
allelic An allele is a variant of the sequence of nucleotides at a particular location, or locus, on a DNA molecule. Alleles can differ at a single position through single nucleotide polymorphisms (SNP), but they can also have insertions and deletions ...
variants and environment may influence
phenotypic In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...
traits.


Where maintained

Some twin registries seek to cover all twins in an entire country, including
Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
,Swedish Twin Registry
accessed 2013-06-14
Denmark Denmark is a Nordic countries, Nordic country in Northern Europe. It is the metropole and most populous constituent of the Kingdom of Denmark,, . also known as the Danish Realm, a constitutionally unitary state that includes the Autonomous a ...
,Danish Twin Registry
accessed 2013-06-14
Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...
, Tambs, Rønning et al.
"The Norwegian Institute of Public Health Twin Study of Mental Health: Examining Recruitment and Attrition Bias"
Twin Res Hum Genet. 2009 April; 12(2): 158–168. doi: 10.1375/twin.12.2.158. Accessed 2013-06-14
Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...
,
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
,Australian Twin Registry
accessed 2013-06-14
Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...
Sri Lankan Twin Registry
accessed 2015-05-15
and the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...
.U.K. Twin Registry
accessed 2013-06-14
The Swedish Twin Registry is the largest twin database in the world, with approximately 85,000 twin pairs. Other twin registries cover a more limited geographic scope and are maintained by researchers at academic institutions, such as the
Michigan State University Twin Registry {{primary sources, date=March 2009 The Michigan State University Twin Registry (or MSUTR) is a registry of twins produced by researchers at Michigan State University. The MSUTR has a lifespan perspective focused on understanding risk factors for ...
, a registry of twins produced by researchers at
Michigan State University Michigan State University (Michigan State or MSU) is a public university, public Land-grant university, land-grant research university in East Lansing, Michigan, United States. It was founded in 1855 as the Agricultural College of the State o ...
, the Washington State Twin Registry,Washington State Twin Registry
accessed 2016-07-11
a registry of twins produced by researchers at
Washington State University Washington State University (WSU, or colloquially Wazzu) is a Public university, public Land-grant university, land-grant research university in Pullman, Washington, United States. Founded in 1890, WSU is also one of the oldest Land-grant uni ...
, and the
Minnesota Twin Registry Minnesota ( ) is a state in the Upper Midwestern region of the United States. It is bordered by the Canadian provinces of Manitoba and Ontario to the north and east and by the U.S. states of Wisconsin to the east, Iowa to the south, and Nor ...
project by researchers at the
University of Minnesota The University of Minnesota Twin Cities (historically known as University of Minnesota) is a public university, public Land-grant university, land-grant research university in the Minneapolis–Saint Paul, Twin Cities of Minneapolis and Saint ...
related to the
Minnesota Twin Family Study The Minnesota Center for Twin and Family Research (MCTFR) is a series of behavioral genetic longitudinal studies of families with twin or adoptive offspring conducted by researchers at the University of Minnesota. It seeks to identify and charact ...
. The largest twin registry in the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
is the Mid-Atlantic Twin Registry (MATR) at
Virginia Commonwealth University Virginia Commonwealth University (VCU) is a Public university, public research university in Richmond, Virginia, United States. VCU was founded in 1838 as the medical department of Hampden–Sydney College, becoming the Medical College of Virgin ...
, which has more than 51,000 registered participants, with approximately 46,000 of these representing intact twin pairs.


Limitations

Many twin registries depend on the voluntary participation of twins – that is, participation in these twin registries is not compulsory, and twins must voluntarily elect whether or not to register with a twin registry (and later, whether to participate in research projects). This characteristic limitation of many twin registries leads to standard issues known as "recruitment bias" or "volunteer bias". D. T. Lykken, M. McGue, A. Tellegen
"Recruitment bias in twin research: The rule of two-thirds reconsidered"
Behavior Genetics:vol. 17, no. 4, pp. 343-362, 1987. DOI: 10.1007/BF01068136 Accessed 2013-06-14
Recruitment biases include an over-inclusion of twins who share similar characteristics, and over-inclusion of identical twins and female twins: D. T. Lykken, A. Tellegen & R. DeRubeis
"Volunteer bias in twin research: The rule of two‐thirds"
Biodemography and Social Biology:Volume 25, Issue 1, 1978. Accessed 2013-06-14
:" is recruitment bias ... results in ... overestimation of the true heritability of the trait under study." Twin registries use a number of strategies to try to reduce the risk of recruitment bias. Some twin registries are "mandatory" - that is, for example, under the public health laws of Norway, all births of twins since 1967 have been recorded in a twin registry maintained by the Norwegian government. By comparison, enlisting with the Australian Twin Registry is voluntary.Australian Twin Registry registration
"With over 70,000 members the ATR has become the largest volunteer registry of multiples in the world. Nevertheless, this still only represents about 10% – 15% of twins in Australia and we need more recruits!" Accessed 2013-06-16.
While the twin registry in Sri Lanka is based on volunteer twins, that twin registry has made extensive out-reach efforts, such as examining hospital birth records, and then making multiple follow-up efforts (including in-person visits) to find the twins and have them (or their parents) agree to be registered. Siribaddana SH, Siriwardane WD, et al
"Update from Sri Lankan Twin Registry"
Twin Res Hum Genet. 2006 Dec;9(6):868-74.


Footnotes

{{reflist Genetics databases Registry