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Dizygotic Twins (dizygotic + twin)
Terms modified by Dizygotic Twins Selected AbstractsCongenital Malalignment of the Great Toenails in Dizygotic TwinsPEDIATRIC DERMATOLOGY, Issue 5 2005Sadiye Kus M.D. It may cause onychogryphosis and, in infants and children, ingrown nails. We report an occurrence of this deformity in dizygotic twins [source] Nonlinear epigenetic variance: review and simulationsDEVELOPMENTAL SCIENCE, Issue 1 2010Kees-Jan Kan We present a review of empirical evidence that suggests that a substantial portion of phenotypic variance is due to nonlinear (epigenetic) processes during ontogenesis. The role of such processes as a source of phenotypic variance in human behaviour genetic studies is not fully appreciated. In addition to our review, we present simulation studies of nonlinear epigenetic variance using a computational model of neuronal network development. In each simulation study, time series for monozygotic and dizygotic twins were generated and analysed using conventional behaviour genetic modelling. In the results of these analyses, the nonlinear epigenetic variance was subsumed under the non-shared environmental component. As is commonly found in behaviour genetic studies, observed heritabilities and unique environmentabilities increased with time, whereas common environmentabilities decreased. The fact that the phenotypic effects of nonlinear epigenetic processes appear as unsystematic variance in conventional twin analyses complicates the identification and quantification of the ultimate genetic and environmental causes of individual differences. We believe that nonlinear dynamical system theories provide a challenging perspective on the development of individual differences, which may enrich behaviour genetic studies. [source] Are there genetic influences on addiction: evidence from family, adoption and twin studiesADDICTION, Issue 7 2008Arpana Agrawal ABSTRACT Aims In this exciting era of gene discovery, we review evidence from family, adoption and twin studies that examine the genetic basis for addiction. With a focus on the classical twin design that utilizes data on monozygotic and dizygotic twins, we discuss support in favor of heritable influences on alcohol, nicotine, cannabis and other illicit drug dependence. Methods We review whether these genetic factors also influence earlier stages (e.g. experimentation) of the addictive process and whether there are genetic influences specific to each psychoactive substance. Results Converging evidence from these studies supports the role of moderate to high genetic influences on addiction with estimates ranging from 0.30 to 0.70. The changing role of these heritable factors as a function of gender, age and cultural characteristics is also discussed. We highlight the importance of the interplay between genes and the environment as it relates to risk for addiction and the utility of the children-of-twins design for emerging studies of gene,environment interaction is presented. Conclusions Despite the advances being made by low-cost high-throughput whole genome association assays, we posit that information garnered from twin studies, especially extended twin designs with power to examine gene,environment interactions, will continue to form the foundation for genomic research. [source] Genetic and environmental determinants of temperament: a comparative study based on Polish and German samplesEUROPEAN JOURNAL OF PERSONALITY, Issue 3 2003odzimierz Oniszczenko This study of 1555 adult mono- and dizygotic twins reared together estimates the heritability of temperament traits in a Polish and a German sample. We test whether the etiology of temperament traits differs between the two cultures and between different temperament traits. We assessed temperament traits with the Formal Characteristics of Behaviour,Temperament Inventory (FCB-TI), the Pavlovian Temperament Survey (PTS), the Revised Dimensions of Temperament Survey (DOTS-R), and the Emotionality,Activity,Sociability Temperament Survey (EAS-TS). Taking error of measurement into account, genetic sources of variance explained about 50% of the variance of temperament traits. We found neither reliable cultural differences nor robust differences in the etiology of the traits. However, the four questionnaires differed systematically with respect to the proportion of genetic and environmental influences on their scales. Copyright © 2002 John Wiley & Sons, Ltd. [source] Genetic and environmental influences on Anxious/Depression during childhood: a study from the Netherlands Twin RegisterGENES, BRAIN AND BEHAVIOR, Issue 8 2005D. I. Boomsma For a large sample of twin pairs from the Netherlands Twins Register who were recruited at birth and followed through childhood, we obtained parental ratings of Anxious/Depression (A/D). Maternal ratings were obtained at ages 3 years (for 9025 twin pairs), 5 years (9222 pairs), 7 years (7331 pairs), 10 years (4430 pairs) and 12 years (2363 pairs). For 60,90% of the pairs, father ratings were also available. Multivariate genetic models were used to test for rater-independent and rater-specific assessments of A/D and to determine the genetic and environmental influences on individual differences in A/D at different ages. At all ages, monozygotic twins resembled each other more closely for A/D than dizygotic twins, implying genetic influences on variation in A/D. Opposite sex twin pairs resembled each other to same extent as same-sex dizygotic twins, suggesting that the same genes are expressed in boys and girls. Heritability estimates for rater-independent A/D were high in 3-year olds (76%) and decreased in size as children grew up [60% at age 5, 67% at age 7, 53% at age 10 (60% in boys) and 48% at age 12 years]. The decrease in genetic influences was accompanied by an increase in the influence of the shared family environment [absent at ages 3 and 7, 16% at age 5, 20% at age 10 (5% in boys) and 18% at age 12 years]. The agreement between parental A/D ratings was between 0.5 and 0.7, with somewhat higher correlations for the youngest group. Disagreement in ratings between the parents was not merely the result of unreliability or rater bias. Both the parents provided unique information from their own perspective on the behavior of their children. Significant influences of genetic and shared environmental factors were found for the unique parental views. At all ages, the contribution of shared environmental factors to variation in rater-specific views was higher for father ratings. Also, at all ages except age 12, the heritability estimates for the rater-specific phenotype were higher for mother ratings (59% at age 3 and decreasing to 27% at age 12 years) than for father ratings (between 14 and 29%). Differences between children, even as young as 3 years, in A/D are to a large extent due to genetic differences. As children grow up, the variation in A/D is due in equal parts to genetic and environmental influences. Anxious/Depression, unlike many other common childhood psychopathologies, is influenced by the shared family environment. These findings may provide support for why certain family therapeutic approaches are effective in the A/D spectrum of illnesses. [source] Lifetime Prevalence and Characteristics of Recurrent Primary Headaches in a Population-Based Sample of Swedish TwinsHEADACHE, Issue 8 2002Dan A. Svensson MSc Objective.,To examine the lifetime prevalence and other characteristics of recurrent primary headaches in twins. Background.,The twin model may provide insights into the role of genetic and environmental influences in headache disorders. However, assumptions as to whether twins are representative of the general population, and whether monozygotic and dizygotic twins are similar have rarely been addressed. Methods.,The study population consisted of a random sample of 17- to 82-year-old twins from the Swedish Twin Registry (n = 1329). Structured interviews on the telephone by lay personnel and the International Headache Society criteria were used for assessment and diagnosis of recurrent primary headaches. Prevalence data of the general population for migraine and tension-type headache was obtained from various published reports. Results.,A total of 372 subjects (29%) had ever had recurrent headaches. In total, 241 recurrent headache sufferers fulfilled the criteria for migraine or tension-type headache, and the lifetime prevalence was 7.1% for migraine without aura, 1.4% for migraine always with aura, 1.9% for migraine occasionally with aura, 9.4% for episodic tension-type headache, and 1.3% for chronic tension-type headache. The lifetime prevalence of all migraine and all tension-type headache, including another 84 subjects fulfilling all but one of the criteria for migraine or tension-type headache, was 13.8% and 13.5%, respectively. The corresponding prevalence risk for women was 2.4 (95% confidence interval [CI] 1.7, 3.4) and 1.5 (95% CI 1.1, 2.1), respectively. Zygosity was not a significant predictor for migraine. In tension-type headache, the prevalence risk for dizygotic twins and unlike-sexed twins as compared with monozygotic twins was 1.9 (95% CI: 1.2, 3.1) and 1.8 (95% CI: 1.1, 2.9), respectively. Conclusion.,There is no twin-singleton or monozygotic-dizygotic difference for the risk of migraine. In tension-type headache, twins seem to have a lower risk than singletons, and this is especially true for monozygotic twins. [source] An examination of the overlap between genetic and environmental risk factors for intentional weight loss and overeatingINTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 6 2009Tracey D. Wade PhD Abstract Objective: To further our understanding of how intentional weight loss (IWL) and overeating are related, we examined the shared genetic and environmental variance between lifetime IWL and overeating. Method: Interview data were available for 1,976 female twins (both members of 439 and 264 pairs of monozygotic and dizygotic twins, respectively), mean age = 40.61, SD = 4.72. We used lifetime diagnostic data for eating disorders obtained from a semistructured psychiatric telephone interview, examined in a bivariate twin analysis. Both lifetime behaviors were measured on a 3-point scale, where absence of IWL or overeating formed one anchor on the scale and lifetime anorexia nervosa (AN) and bulimia nervosa (BN) formed the opposite anchors, respectively. Results: In line with previous findings, a higher body mass index was significantly associated with the lifetime presence of IWL and/or overeating (odds ratio = 1.13, 95% confidence interval (CI): 1.08,1.19). The best fitting twin model contained additive genetic and nonshared environmental influence influencing both IWL and overeating, with correlations between these influences of 0.61 (95% CI: 0.35,0.92) and 0.24 (95% CI: 0.07,0.42), respectively. Discussion: About 37% of genetic risk factors were considered to overlap between IWL and overeating, and with only 6% of overlap between environmental risk factors. Thus, considerable independence of risk factors was indicated. © 2009 by Wiley Periodicals, Inc. Int J Eat Disord 2009 [source] The Twin Inventory of Relationships and Experiences (TIRE): psychometric properties of a measure of the non-shared and shared environmental experiences of twins and singletonsINTERNATIONAL JOURNAL OF METHODS IN PSYCHIATRIC RESEARCH, Issue 2 2001Rene Carbonneau Abstract We examined longitudinally the psychometric properties of the Twin Inventory of Relationships and Experiences (TIRE), an instrument designed to assess non-shared and shared environmental experiences in twins and siblings. A community sample of 1,117 pairs of like-sex monozygotic and dizygotic twins, aged eight to 16, and their parents, was used. Results indicated that the TIRE provided constructs that are consistent across informants, gender and time. These dimensions showed good longitudinal stability within raters, and low to moderate inter-rater agreement; the results are consistent with those of other studies using different instruments to assess family environment. It is concluded that the TIRE may be used to assess dimensions of the non-shared environment of twins and siblings and their influence on children's development. Copyright © 2001 Whurr Publishers Ltd. [source] Body mass index, alcohol, tobacco and symptomatic gallstone disease: a Swedish twin studyJOURNAL OF INTERNAL MEDICINE, Issue 5 2007D. Katsika Abstract. Background/Aims., Both genetic and environmental factors are involved in the pathogenesis of gallstone disease (GD). We aimed to examine the association between symptomatic GD and overweight (body mass index, BMI, 25,30 kg m,2), obesity (BMI > 30 kg m,2), alcohol, smoking and smoke-free tobacco by analysing a large twin population. Methods., The Swedish Twin Registry (STR) was linked to the Swedish Hospital Discharge and Causes of Death Registries for GD and GD-surgery related diagnoses. Weight, height, use of alcohol, smoking and smoke-free tobacco were provided by STR and analysed for possible associations by conditional logistic regression. Results., Overweight and obesity were associated with a significantly higher risk for symptomatic GD in the whole study population (OR 1.86 and OR 3.38; CI: 1.52,2.28 and 2.28,5.02 respectively). High alcohol consumption was associated with a lower risk for GD in the whole population (OR 0.62; CI: 0.51,0.74) with no difference between discordant monozygotic and dizygotic twins (OR 1.08 and OR 0.96; CI: 0.82,1.42 and 0.79,1.16). Smoking or smoke-free tobacco was not correlated with GD. Conclusion., Consistent with epidemiological studies, we found positive associations between BMI and the development of symptomatic GD. High alcohol consumption was associated with a decreased risk against GD. Tobacco use has no impact on GD. [source] Sociability and Positive Emotionality: Genetic and Environmental Contributions to the Covariation Between Different Facets of ExtraversionJOURNAL OF PERSONALITY, Issue 3 2003Michael Eid The relation between sociability and positive affect is one of the most often replicated results of research on personality and subjective well-being. It is shown how behavior genetics can contribute to our understanding of the covariance between sociability and positive emotionality. The results of a multimethod behavior-genetic study with 158 monozygotic and 120 dizygotic twins are reported. In this study, sociability and two components of positive emotionality (positive affect, energy) were assessed by self-report and other report. Additionally, positive state affect was assessed in five situations and aggregated across situations. The results showed that there are strong genetic correlations between all variables. Furthermore, there are substantive correlations between the nonshared environmental components of the different variables. Shared environmental influences, however, seemed to be unimportant for explaining the correlations between sociability and the different components of positive emotionality. The results are discussed with respect to their implications for future research on sociability and positive emotionality. [source] Influence of genetics on irritable bowel syndrome, gastro-oesophageal reflux and dyspepsia: a twin studyALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 11 2007A. LEMBO Summary Background A genetic contribution has been proposed for irritable bowel syndrome (IBS) and gastro-oesophageal reflux disease (GERD), but is controversial. No twin data exist for dyspepsia. Aim To determine the relative contribution of genetic factors in GERD, dyspepsia (upper abdominal pain) and IBS. Methods A total of 986 twin pairs (from initial mail-out response 51%). Both members completed validated symptom and psychological questionnaires; 481 monozygotic pairs [mean (s.d.) age 53 ± 5.8 years] and 505 dizygotic pairs (mean age 54 ± 5.6 years). Results Prevalence of IBS, dyspepsia and GERD was 12%, 10% and 20%, respectively. Polychoric correlation for monozygotic twins for IBS (0.47) and GERD (0.44) were both substantially larger than those for dizygotic twins (0.17 and ,0.37, respectively). Polychoric correlation was slightly lower in monozygotic than dizygotic twins for dyspepsia. Genetic modelling confirmed the independent additive genetic effects in GERD and IBS but not dyspepsia. Estimates of genetic variance were 22% for IBS, 13% for GERD and 0% for dyspepsia, but adjusting for anxiety and depression removed the statistical significance for IBS and GERD. Conclusions There is a genetic contribution to GERD and IBS but not dyspepsia; this may be mediated by the hereditability of anxiety and depression. [source] A quantitative genetic study of cephalometric variables in twinsORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 3 2001C. Carels This study aimed at determining the relative genetic and environmental impact on a number of well-known cephalometric variables in twins. In order to find a clue in the heritability pattern of some dentofacial characteristics and on the expected limits of the therapeutic impact on the dentofacial subparts they are representing. Cephalograms were collected from 33 monozygotic and 46 dizygotic twins, who did not undergo any orthodontic treatment. Nineteen linear and four angular variables were selected all representing a different definite subpart of the dentofacial complex. The reproducibility of the measurement of most of the linear variables was very high. A genetic analysis using model fitting and path analysis was carried out. First, data were checked on the fulfilment of the conditions for genetic analysis in twins reared together. The results show that the genetic determination is significantly higher for vertical (72%) than for horizontal (61%) variables. As far as the genetic component is concerned, all variables selected seem to be inherited by additive genes, except for mandibular body length, which was determined by dominant alleles. Sex differences in genetic determination were found for the anterior face height, showing a significantly higher genetic component for boys (91%) than for girls (68%). For the angular measurements, no genetic influence was found: only environmental influences common to both members of each pair could be demonstrated. [source] Studies of twins: what can they tell us about the fetal origins of adult disease?PAEDIATRIC & PERINATAL EPIDEMIOLOGY, Issue 2005Ruth Morley Summary There has been much interest in evidence that people with lower birthweight have higher risk of adult cardiovascular disease, but the causal pathways underlying such observations are uncertain. Study of twins offers an opportunity to shed light on the underlying causal pathways, in particular by investigating the role of ,shared' factors vs. factors affecting each individual fetus. This involves comparing results of within-cohort vs. within-pair analyses. Twins share many factors during gestation but birthweight discordance (difference in birthweight within a twin pair) cannot be determined by these shared factors and must relate to factors affecting growth of each individual fetus. If associations seen in a cohort of twins remain in within-pair analyses, then factors specific to each individual must be involved in the underlying causal pathways. Conversely, if the relationships disappear or substantially diminish in within-pair analyses, then factors common to the pair must be involved. Comparison of findings in monozygotic vs. dizygotic twins may provide insights into the role of genetic factors, although issues related to chorionicity need to be taken into account. We tabulate published data and conclude that differences in methodology and analyses preclude informative meta-analysis, and that analysis of pooled data would provide more useful information. [source] Congenital Malalignment of the Great Toenails in Dizygotic TwinsPEDIATRIC DERMATOLOGY, Issue 5 2005Sadiye Kus M.D. It may cause onychogryphosis and, in infants and children, ingrown nails. We report an occurrence of this deformity in dizygotic twins [source] Non-identical monozygotic twins, intermediate twin types, zygosity testing, and the non-random nature of monozygotic twinning: A review,AMERICAN JOURNAL OF MEDICAL GENETICS, Issue 2 2009Geoffrey Machin Abstract Monozygotic twins (MZ) are rarely absolutely "identical." This review discusses the types of genetic/epigenetic and prenatal environmental post-zygotic mechanisms that cause discordance within such twin pairs. Some of these mechanisms,ranging from heterokaryotypia to skewed X-chromosome inactivation,may cause extreme discordance, but these extremes are merely the more emphatic examples of discordance that, to some degree, underlies the majority of MZ twin pairs. Because of the entrenched misconception that MZ twins are necessarily identical, many MZ twin pairs are mistakenly designated as dizygotic (DZ). Clinical benefits to accurate zygosity determination include correct solid organ transplantation matching, if one twin requires donation for a non-genetically mediated disease; the opportunity of preventive management for disorders that do not manifest synchronously; and better counseling to parents regarding their individually unique, and often psychologically puzzling, twin offspring. In twin pairs with complex and confusing biological origins, more detailed zygosity testing may be required. For example, intermediate trigametic and tetragametic chimeric dizygotic twins are reviewed, some of whom are, nevertheless, monochorionic (MC). Because of inter-fetal vascular anastomoses in MC twins, genetic results from blood samples may not accurately reflect discordance in solid organs. Previously, it was thought that MZ twinning was some sort of embryological fluke. However, familial monozygotic twinning is more common than suggested by the literature. Seven new families are presented in an accompanying paper. Despite the difficulties and dangers of twin pregnancy (especially so for MC twins), human twinning persists, and continues to both challenge and fascinate parents, clinicians and geneticists. © 2009 Wiley-Liss, Inc. [source] Selected neonatal outcomes in dizygotic twins after IVF versus non-IVF pregnanciesBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 6 2010B Källén Please cite this paper as: Källén B, Finnström O, Lindam A, Nilsson E, Nygren K-G, Otterblad Olausson P. Selected neonatal outcomes in dizygotic twins after IVF versus non-IVF pregnancies. BJOG 2010; Objective, To compare neonatal outcome among twins conceived after in vitro fertilisation (IVF) with that of spontaneously conceived twins. Design, Comparison of different-sex (dizygotic) twins born after IVF with non-IVF dizygotic twins. Setting, National health registers in Sweden. Population, All births in Sweden during the period 1982,2007. Methods, We studied gestational duration, lowest birthweight and birthweight difference in the twin pair, presence of one or two twins with a respiratory complication, and with jaundice in one or both twins. Risk estimates were calculated as odds ratios with adjustments for year of birth, maternal age, parity and smoking in pregnancy. Main outcome measures, Gestational duration, birth weight, respiratory complications, jaundice. Results, We studied 1545 pairs of dizygotic twins born after IVF, and 8675 pairs of dizygotic twins where IVF was not known to have occurred. The risk for preterm delivery before 32 weeks of gestation was significantly increased among dizygotic twin pairs born after IVF compared with non-IVF dizygotic twin pairs. No significant difference in low birthweight or birthweight difference within twin pairs was seen. There was an increased occurrence of twin pairs with respiratory problems or jaundice, but only the latter diagnosis occurred in a statistically significant excess. Conclusions, The study confirms recent findings that IVF is associated with an increased risk for some neonatal complications, not only among singletons but also among twins. [source] Neonatal management of symptomatic transplacental cryoglobulinaemiaACTA PAEDIATRICA, Issue 4 2004V Laugel This study reports the first case of symptomatic placental transfer of cryoglobulins and discusses the potential pathogenic processes and the basic guidelines for neonatal management. A 32-y-old woman was affected by essential type I cryoglobulinaemia and displayed the cold-triggered cutaneous symptoms of the disease due to a monoclonal immunoglobulin G (IgG) cryoglobulin. She gave birth to healthy dizygotic twins who were placed in incubators immediately after birth and did not show any cutaneous or visceral lesion in the first 2 d. Cyanotic macules appeared on the hand and foot of one of the newborns when they were removed from the incubators. The same monoclonal IgG-, cryoglobulin was identified in the two newborns'cord blood and in the mother's serum. The skin lesions disappeared within 1 wk as both twins were transiently replaced in incubators. No recurrence of skin lesions was observed even at room temperature and, 6 mo later, both twins were healthy and their clinical examination was normal. Conclusion: To the authors'knowledge, this is the first report of placental transfer of cryoglobulins and the first description of any neonatal effect. Neonates born to mothers suffering from IgG cryoglobulinaemia should be protected against cold to avoid precipitation of the pathogenic cryoglobulins, until spontaneous resolution. [source] | ||||||||||||||||