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Topic: Twin study

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Twin

Heritability

Nature versus nurture

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	Twin study - Wikipedia, the free encyclopedia
		A twin study is a kind of genetic study done to determine heritability.
		The premise is that since identical twins (especially identical twins raised apart) have identical genotypes, differences between them are solely due to environmental factors.
		By examining the degree to which twins are differentiated, a study may determine the extent to which a particular trait is influenced by genes or the environment.
	en.wikipedia.org /wiki/Twin_study (386 words)

	Twin studies
		Today, medical researchers are increasingly recognising the power of the twin study model, combined with new gene technologies, to tease out the genetic bases for a range of common but complex diseases, such as cancer, heart disease, arthritis and diabetes.
		Twin studies use comparisons between identical and non-identical twins to explore the contributions of genetic and environmental factors in health and disease.
		Studying identical twins alone is less useful, since they share not only all their genes but also their, birthdate, uterine and early environment, schooling and family background.
	www.wellcome.ac.uk /en/genome/genesandbody/hg08b001.html (510 words)

	Twin study -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-09-06)
		A twin study is a kind of (Click link for more info and facts about genetic) genetic study done to determine (Click link for more info and facts about heritability) heritability.
		The premise is that since identical ((mineralogy) two interwoven crystals that are mirror images on each other) twins (especially identical twins raised apart) have identical (A group of organisms sharing a specific genetic constitution) genotypes, differences between them are solely due to environmental factors.
		Also, there are different ways of calculating concordance (the presence of a similar disease (What an organism looks like as a consequence of its genotype; two organisms with the same phenotype can have different genotypes) phenotype in twins) which can give markedly different results.
	www.absoluteastronomy.com /encyclopedia/t/tw/twin_study.htm (363 words)

	UMN Dept of Psychology: MTFS
		Its original goal was to establish a registry of all twins born in Minnesota from 1936 to 1955 for psychological research.
		From this project, we were able to confirm that twins and their families are representative of the population and that a poll of their opinions would be more accurate than polls in the newspaper.
		He is also PI on an epidemiological study of first-episode schizophrenia, and he is currently co-investigator with William Grove on a family study of schizophrenia (NIMH 49738) in which psychophysiological measures are being used to characterize familial transmission in schizophrenia.
	www.psych.umn.edu /psylabs/mtfs (757 words)

	Upstream: Upstream: Issues: Psychology: IQ: Minnesota Twins (Site not responding. Last check: 2007-09-06)
		Rearing SES effects on IQ in adoption studies have been found for young children but not in adult samples [21], suggesting that although parents may be able to affect their children's rate of cognitive skill acquisition, they may have relatively little influence on the ultimate level attained.
		MZA twins share prenatal and perinatal environments, but except for effects of actual trauma, such as fetal alcohol syndrome, there is little evidence that early shared environment significantly contributes to the variance of psychological traits.
		Whereas behavioral geneticists study variatins within a species, evolutionary psychologists or sociobiologists attempt to delineate species-typical proclivities or instincts and to understand the relevant evolutionary developments that took place in the Pleistocene epoch and were adaptive in the lives of tribal hunter-gatherers.
	www.mugu.com /cgi-bin/Upstream/Issues/psychology/IQ/bouchard-twins.html (5107 words)

	Twin Study Evaluates Role of Environmental Stress in Cardiovascular Disease (Site not responding. Last check: 2007-09-06)
		When the twins started the study, their average age was 14; they will be 18, on average, as they start the new study.
		Twins were picked for study because researchers could more easily determine the genetic influence on blood pressure by comparing identical twins who share 100 percent of their genes and fraternal twins who share 50 percent, about the same as any two siblings of the same age.
		In a separate longitudinal study of young African-Americans and European-Americans with a family history of hypertension, the researchers already are finding that the African-Americans are showing telltale signs of blood pressure problems as they move into their late teens and early 20s.
	www.mcg.edu /news/2001NewsRel/twins.html (960 words)

	Prospective twin study ...
		The study was carried out in two specialist centres in the USA and comprised a 12.2-year follow-up (median) for the monozygotic twins and a 5.9-year follow-up for the dizygotic twins.
		The authors conclude that monozygotic and dizygotic twin siblings differ in their progression towards the development of Type 1 diabetes and that genetic rather than environmental factors play a pivotal role in the generation of islet cell autoimmunity.
		Stimulated by a recent paper in Denmark showing that dizygotic twins with islet cell auto-antibodies are at a much lower risk of developing diabetes than their non-twin siblings, the authors studied a large series of twins (both monozygotic and dizygotic) to confirm or reject this measurement of islet cell antibodies.
	www.medforum.nl /idm/prospective_twin_study____.htm (538 words)

	Twin Study Shows New Breast Cancer Risk
		The study, published in the June 5 issue of The New England Journal of Medicine, involved 1,811 sets of identical and nonidentical female twins in which one or both of the twins had breast cancer.
		However, among identical twin pairs in which only one twin had breast cancer, a later first pregnancy, fewer children, and later menopause were associated with an increased risk of breast cancer, but age of puberty was not.
		Therefore, researchers say the study suggests that most cases of hereditary breast cancer are not related to total hormone exposure during a woman's lifetime, but to an unusual susceptibility to the hormonal surge of puberty.
	my.webmd.com /content/article/66/79674 (523 words)

	Twin Studies
		These twins are contacted through the Colorado Twin Registry, which is developed with assistance from the Colorado Departments of Health and Education.
		Community Twin Study (CTS) For this project twins ages 12-18 and their siblings throughout Colorado participate in a 2 1/2 hour interview that covers questions about personality, behavior, intelligence and various mood and conduct disorders.
		Longitudinal Study of Early Reading Development (LSERD) This study, a collaborative effort with the University of New England in Australia and Stavanger University in Norway, is designed to study genetic and environmental influences on early reading and attention development.
	ibgwww.colorado.edu /~agross/ibg/twinsites.htm (507 words)

	Nature vs. Nuture - Twin Study Overview
		Twin and adoption studies can tell the extent to which family resemblance is due to shared genes and the extent of shared environment.
		This topic has been studied intensely, and many scientists try to use schizophrenia disorder as a means to try to understand why one twin might have the disease and the other might not.
		In her website, www.behavior.org/behaviordigest/v9n1/digest_v9n1_shcizophrenia.cfm she refers to psychiatrist Peter R. Breggin, who believes that the twin studies that have been done to prove that schizophrenia is genetic is wrong.
	www.pages.drexel.edu /~rm35 (1962 words)

	Child Language Research Center
		The twins in this research have either been sampled from the general population and thus represent the full range of normal language development or they were sampled because at least one twin had poor or impaired language development.
		One recent study of twins focused on the comorbidity between poor vocabulary and poor nonverbal cognitive development and found evidence in support of a common set of genes influencing both poor nonverbal cognition and poor vocabulary development (Purcell et al., 2001).
		The twin studies cited earlier, showing that SLI is genetically influenced, have provided an impetus to search for genes that have particular or predominant effects on language.
	www.uiowa.edu /~clrc/genetics/index.html (2899 words)

	Longitudinal Twin Study
		Its purpose is to further research and public education in all fields related to twins and twin studies, for the mutual benefit of twins and their families and of scientific research in general.
		Mid-Atlantic Twin Registry - This site provides information on current and past research projects and results from many of the research projects in which MATR twins and their family members are participating.
		Twin Research and Genetic Epidemiology - This center at St. Thomas' hospital in London studies the genetic and environmental factors associated with aging and lifestyle and inherited causes and effects on disease development.
	ibgwww.colorado.edu /lts/links.htm (657 words)

	Longitudinal Twin Study
		The Colorado Longitudinal Twin Study is an ongoing research project of the Institute for Behavioral Genetics, which is a department of the University of Colorado at Boulder.
		Since that time we have collected data from participating twins and their families on a regular basis, conducting home and lab visits at infancy and ages 7, 12, 16 and 17, and telephone interviews during non-visit years.
		The purpose of this research is to study the varying genetic and environmental influences on development, including cognition, temperament, physical development, intelligence and emotion.
	ibgwww.colorado.edu /lts (254 words)

	Encyclopedia: Twin study
		Fraternal twin boys in the tub The term twin most notably refers to two individuals (or one of two individuals) who have shared the same uterus (womb) and are usually, but not necessarily, born on the same day.
		The genotype is the specific genetic makeup (the specific genome) of an individual, usually in the form of DNA.
		The bust of Posidonius as an older man depects his character as a Stoic philosopher.
	www.nationmaster.com /encyclopedia/Twin-study (668 words)

	Twin Study--Genetics Key Factor In Speech Learning
		A team of American and British researchers studying 2-year-old twins has found that genetics, not the environment, plays the major role in the delayed acquisition of language among children who are having the most difficulty learning to speak.
		The study, which looked at more than 3,000 pairs of twins born in England and Wales, was headed by Robert Plomin, research professor of psychology at the Institute of Psychiatry in London and Philip Dale, University of Washington psychology professor.
		If one identical twin ranked in the lowest 5 percent there was an 81 percent chance that his or her twin also would fall into that group.
	www.sciencedaily.com /releases/1998/10/981023073445.htm (1012 words)

	Twin study
		If you are a twin between the ages of 16 and 80, I would appreciate a few minutes of your time to take part in my twin study on twins.
		If you are interested in the results of this study you may contact me at the address located at the end of the survey.
		I understand this research is being done to study the correlation between being a twin and the development of self-esteem and individual self-identity.
	www.niagara.edu /psychology/osberg/Twin_study.html (689 words)

	Twin Wing Study
		These figures present the results of a parametric study of the key geometry variables in a twin rigid wing rig (some of which are depicted here).
		When compared on the basis of equal rig heights, the twin wing was superior in nearly every respect to a comparable analysis performed on a single wing rig.
		However, the actual performance may differ because of Reynolds number effects (the twin wing's Reynolds number is less than half that of the single wing) and compromises necessay to provide adequate structural stiffness to the twin wing's long, slender panels.
	www.tspeer.com /landyachts/twin/dragstudy.htm (469 words)

	Fertility Neighborhood : Obesity, Not Fertility Drugs, Ups Twin Risk: Study
		The assumption that the increased use of fertility drugs and assisted reproductive technologies (ART) in the past two decades has partly contributed to the increased risk of fraternal twins is erroneous, says a new study.
		The study by researchers at the National Institutes of Health (NIH) suggests that the odds of having fraternal twins in the United States increase as maternal BMI rises.
		In conclusion, the study team wrote: "There has been a marked increase in obesity in the United States, with the proportion of women aged 20 to 39 years with a BMI of 30 or more increasing from 9.3% in the early 1960s to 29.1% in 1999 to 2002."
	www.fertilityneighborhood.com /content/in_the_news/archive_1190.aspx (728 words)

	New Scientist Breaking News - IQ is inherited, suggests twin study
		In identical twins, these areas showed a 95 to 100 per cent correlation between one twin and the other - they were essentially the same.
		Fraternal twins were near-identical in Wernicke's area, showing about 60 to 70 per cent correlation, but were less similar in other areas,.
		The study was all the more interesting in that it found that not only was this gray matter highly heritable, but it affected overall intelligence as well.
	www.newscientist.com /article.ns?id=dn1520 (562 words)

	University of Western Ontario Twin Study Information Form
		In this study we are interested in comparing the relationships that twins have with each other.
		We are also interested in studying twins' relationships with their friends, especially their closest friend of the same sex and their closest friend of the opposite sex.
		If you agree to participate in this study, you will be given a questionnaire package that includes questions about the people in your life who are close to you (acquaintances, friends, and close friends), and your relationship with your twin, your best friend of the same sex and your best friend of the opposite sex.
	publish.uwo.ca /~akfoy/study_info.html (342 words)

	A Twin Study of Chronic Fatigue -- Buchwald et al. 63 (6): 936 -- Psychosomatic Medicine
		successfully in a study of the genetics of homosexuality (28).
		Symptoms of anxiety and depression in a volunteer twin population: the etiologic role of genetic and environmental factors.
		Physical similarity and the equal-environment assumption in twin studies of psychiatric disorders.
	www.psychosomaticmedicine.org /cgi/content/full/63/6/936 (4323 words)

	Psychology: Minnesota Twin Family Study
		A good description of the study can be found in The Minnesota Twin Registry: Some Initial Findings.
		He is currently the PI of a twin study of normal aging (NIA AG 06886), and like Iacono and Lykken, he has had considerable experience directing large scale studies like the MTFS.List of Dr. McGue's Behavioral Genetics-related publications.
		Dr. Iacono is a clinical psychologist and psychophysiologist who has been concerned with the identification and characterization of psychophysiological measures as prospective markers of psychopathology.
	www.psych.umn.edu /research/mtfs.htm (814 words)

	Twin Study Adds Fuel To Marijuana Debate -- Bender 38 (6): 34 -- Psychiatric News
		Findings from a new study of more than 300 sets of twins show that early use of marijuana, independent of genetic background and environment, is associated with later drug use and abuse.
		of a new study have bolstered the theory that marijuana is a
		They studied 311 pairs of same-sex twins in which one twin in
	pn.psychiatryonline.org /cgi/content/full/38/6/34 (849 words)

	Carolina African-American Twin Study of Aging - Bibliography (Site not responding. Last check: 2007-09-06)
		Whitfield, K.E. "Studying Biobehavioral Aspects of Health Disparities among Older Adult Minorities." Journal of Urban Health 82(2 Suppl 3):iii103-iii110.
		Whitfield, K.E. "Behavioral Genetic Studies of Health." In Anderson, N.B. and M.E. Kemeny (Eds.), Encyclopedia of Health and Behavior, Volumes 1 and 2.
		Presented at the Gerontological Society of America's annual meeting in Washington, D.C. Whitfield, K.E. Studying African American twins, you have to find them first: The Carolina African American Twin Study of Aging.
	athens.pop.psu.edu /cpha/caatsa-bib.cfm (1002 words)

	Twins_Study_Harvard
		The Twins Study @ Harvard is a long-term study of language development in twins, supervised by Jennifer Ganger, Ph.D., and Professor Steven Pinker, Ph.D.
		The goal of the project is to study identical and fraternal twins to determine the relative importance of nature and nurture in language development.
		Twins Study @ Harvard Supervisor - Steven Pinker
	twins.wjh.harvard.edu (214 words)

	Twin Sisters Study Shows Important Link Between Delivery Mode, Risk of Incontinence - Evanston Northwestern Healthcare (Site not responding. Last check: 2007-09-06)
		In this internationally recognized, award-winning study of identical twin sisters, Dr. Goldberg found that the rate of stress urinary incontinence was three-fold higher after vaginal childbirth compared to cesarean.
		"This study of identical twin sisters shows that mode of delivery has a fundamental impact on a woman's risk of incontinence.
		It is clear that a woman's decision between vaginal and cesarean birth may have important physical repercussions." Despite the findings, Dr. Goldberg cautions, "Cesarean delivery by choice remains a complex issue relating to many physical and psychological factors, which should be carefully discussed between a woman and her doctor.
	www.enh.org /aboutus/press/article.asp?id=2907 (232 words)

	Twin Relationships Study (Site not responding. Last check: 2007-09-06)
		This study investigates interpersonal relationships among siblings and twins.
		As part of the study, individuals who have a twin or sibling complete online questionnaires about their interpersonal relationships.
		I would like all participants to know that I am dedicated to the scientific study of twin relationships and greatly appreciate your participation.
	www.twinsfoundation.com /studies/twin_relationships_study.htm (209 words)

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