Twin Studies as Topic

Publication Title: 
Annals of the New York Academy of Sciences

To live beyond the octogenarian years, population and molecular genetic studies of centenarian sibships indicate that genetic factors play an increasingly important role as the limit of life span is approached. These factors are likely to influence basic mechanisms of aging that in turn broadly influence susceptibility to age-related illnesses. Lacking genetic variations that predispose to disease as well as having variations that confer disease resistance (longevity enabling genes) are probably both important to achieving exceptional old age.

Author(s): 
Perls, Thomas
Publication Title: 
Experimental Gerontology

Centenarians exist at the extreme of life expectancy and are rare. A number of pedigree and molecular genetic studies indicate that a significant component of exceptional longevity is genetically influenced. Furthermore, the recent discovery of a genetic locus on chromosome 4 indicates the powerful potential of studying centenarians for genetic factors that significantly modulate aging and susceptibility to age-related diseases. These studies include siblings and children of centenarians.

Author(s): 
Perls, Thomas
Terry, Dellara
Publication Title: 
Psychiatrische Praxis

There is compelling evidence from family, twin and adoption studies of a substantial genetic contribution to schizophrenia. The mode of transmission is complicated and very rarely if ever involves a single gene. Rather schizophrenia results from multiple genes of small effect and their interplay with the environment. Perhaps because the overall size of the genetic effect is large, accounting for about 80 % of variance, definite environmental factors have been difficult to pin down.

Author(s): 
McGuffin, Peter
Publication Title: 
Molecular Psychiatry

Classical twin research focused on differentiating genetic factors from environmental factors by comparing the concordance rate between monozygotic (MZ) and dizygotic twins. On the other hand, recent twin research tries to identify genetic or epigenetic differences between MZ twins discordant for mental disorders. There are a number of reports of MZ twins discordant for genetic disorders caused by genetic or epigenetic differences of known pathogenic genes.

Author(s): 
Kato, T.
Iwamoto, K.
Kakiuchi, C.
Kuratomi, G.
Okazaki, Y.
Publication Title: 
Schizophrenia Research

The case for replacing the binary Kraepelinian system with a continuum concept originated with Kraepelin [Kraepelin, E. (1920) Die Erscheinungsformen des Irreseins (translated by H Marshall as: Patterns of mental disorder. In: Themes and Variations in European Psychiatry. Eds S.R. Hirsch & M. Shepherd. Wright, Bristol, pp7-30, l974). Zeitschrift Gesamte Neurologie Psychiatrie, vol. 62, 1-29.], and is based upon studies of familial aggregation and phenomenology. Craddock and Owen's [Craddock, N.J., Owen, M.J.

Author(s): 
Crow, T. J.
Publication Title: 
American Journal of Medical Genetics. Part C, Seminars in Medical Genetics

Classical twin studies in the field of psychiatry generally fall into one of two categories: (1) those designed to identify environmental risk factors causing discordance in monozygotic (MZ) twins and (2) those geared towards identifying genetic risk factors. However, neither environment nor differences in DNA sequence can fully account for phenotypic discordance among MZ twins. The field of epigenetics--DNA modifications that can affect gene expression--offers new models to understand discordance in MZ twins.

Author(s): 
Haque, F. Nipa
Gottesman, Irving I.
Wong, Albert H. C.
Publication Title: 
Nature Reviews. Genetics

The classical twin study has been a powerful heuristic in biomedical, psychiatric and behavioural research for decades. Twin registries worldwide have collected biological material and longitudinal phenotypic data on tens of thousands of twins, providing a valuable resource for studying complex phenotypes and their underlying biology. In this Review, we consider the continuing value of twin studies in the current era of molecular genetic studies.

Author(s): 
van Dongen, Jenny
Slagboom, P. Eline
Draisma, Harmen H. M.
Martin, Nicholas G.
Boomsma, Dorret I.
Publication Title: 
Twin Research and Human Genetics: The Official Journal of the International Society for Twin Studies

Over the past decade, epigenetic analyses have made important contributions to our understanding of healthy development and a wide variety of adverse conditions such as cancer and psychopathology. There is increasing evidence that DNA methylation is a mechanism by which environmental factors influence gene transcription and, ultimately, phenotype. However, differentiating the effects of the environment from those of genetics on DNA methylation profiles remains a significant challenge.

Author(s): 
Chiarella, Julian
Tremblay, Richard E.
Szyf, Moshe
ProvenÁal, Nadine
Booij, Linda
Publication Title: 
Twin Research: The Official Journal of the International Society for Twin Studies

Twin research offers the greatest power for the genetic analysis of complex multifactorial traits and diseases in humans. Modern twin analyses extend beyond the classical twin study for estimating the heritability of a trait. The human genome project can fulfil its promises only after functional characterisation of single genes in the context of genetic background and environment. Twin research can make a major contribution in that regard. Twin research is greatly facilitated by the willingness, motivation, cooperation, and generosity of the participants and their families.

Author(s): 
Busjahn, Andreas
Publication Title: 
Twin Research and Human Genetics: The Official Journal of the International Society for Twin Studies

A unique case of artificially conceived twins is described. The infants involved are unrelated to one another, as well as to the mother who carried them. The question of whether these individuals meet scientific criteria for being twins is considered, as is the issue of whether their parents are really parents of twins. Next, the International Society for Twin Studies acknowledges the life and work of its late esteemed colleague, Dr Robert Derom.

Author(s): 
Segal, Nancy L.

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