Dizygotic Twins Research Articles

Molecular confirmation of twinning in the West Indian Manatee (Trichechus manatus)

Abstract: Few twinning events have been recorded in the West Indian manatee (Trichechus manatus, Sirenia: Trichechidae) and no previous published study has provided confirmation of this phenomenon based in molecular tools. Here we investigate a possible case of twinning in an endangered Brazilian population of T. manatus using molecular tools. We analyzed two male neonates found stranded in Ceará State, on the northeastern coast of Brazil. The DNA of both individuals was isolated, and 10 microsatellite loci were amplified and genotyped. Following the identification of the alleles, the probabilities of identity by descent (∆7 and ∆8) and relatedness (rxy) were calculated using estimators that evaluate inbreeding. The two individuals shared most of the alleles, with differences in the genotypes being identified in only two loci. All the estimators identified a level of relatedness compatible with that found between siblings (selfed or outbred), indicating they were dizygotic twins. This is the first confirmed case of fraternal twins in free-ranging West Indian manatees in South America. The recognition of this type of twinning provides elements to improve actions for the rehabilitation of stranded animals and their subsequent release to the environment.

Evidence of familial confounding of the association between cannabis use and cerebellar-cortical functional connectivity using a twin study

Cerebellar-cortical resting-state functional connectivity (rsFC) has been reported to be altered in cannabis users. However, this association may be due to genetic and environmental confounding rather than a causal relationship between cannabis use and changes in rsFC. In this co-twin control study, linear mixed models were used to assess relationships between the number of lifetime cannabis uses (NLCU) and age of cannabis onset (ACO) with cerebellar-cortical rsFC. The rsFC with seven functional networks was evaluated in 147 monozygotic and 82 dizygotic twin pairs. Importantly, the use of genetically informed models in this twin sample facilitated examining whether shared genetic or environmental effects underlie crude associations between cannabis measures and connectivity. Individual-level phenotypic analyses (i.e., accounting for twin-pair non-independence) showed that individuals in the full sample with earlier ACO and higher NLCU had lower cerebellar rsFC within the VA, DA, and FP networks. Yet, there were no significant differences in cerebellar-cortical rsFC between monozygotic twins who were discordant for cannabis measures. These findings suggest shared genetic or environmental confounds contribute to associations between cannabis use and altered cerebellar-cortical rsFC, rather than unique causal impacts of cannabis use on cerebellar-cortical rsFC.

Heritability of Dental Caries: Twin Studies.

The study of twins is a powerful tool to infer the presence and amount of contribution of genetic variation to a particular trait or disease. The ability to compare identical or monozygotic twins with dizygotic twins permits the direct comparison of pairs of individuals that share 100% of their genomic DNA with pairs that share only 50%, with the assumption that these pairs are under the same environment. In the case of dental caries, the environment is same parents, under the same roof, with the same diet, oral hygiene habits, culture, and lifestyle. These data have consistently suggested that a relevant proportion of the variation of dental caries in populations is due to genetics.

Twinning rates in Chennai, India - A cross-sectional study.

Context:The city of Chennai is one of the largest metropolitan cities in India where apart from a large traditional population, there has been a continuous migration from rural areas and growing sophistication in lifestyle. Twinning rates trend in the present world would be interesting to study.Aims:The aim of the present study was to analyse the twinning rate in the city of Chennai, the distribution amongst various city zones and the present trends in the co-relation between the maternal age of the twins with the zygosity.Settings and Design:A population-based study was conducted on twin births in various corporation Zones in the Chennai Metropolitan, between 2010 and 2012. As per the Chennai corporation and Health Department register, there were a total of 2,32,884 births registered in the city of which 4,500 were twin births over the 3 years. Only 1371 pairs were found residing in Chennai at the time of study, and hence, a study was conducted on this population only.Satistical Analysis Used:The data were analysed with Epiinfo software.Results:A twining rate of 19.3 per 1000 births was observed as per Corporation records. In the present study, the sample of 150 pairs, 34 pairs (22.6%) comprised of monozygotic (MZ) twins and 116 pairs (77.3%) comprised of dizygotic twins giving a ratio of 1:3. The maternal age groups 25–30 and 30–35 years comprised of the maximum twinning rates. Most twin births were of the first order. An analysis of Weinberg’s Differential Rule method to determine zygosity showed a significant difference compared to the Questionnaire method.Conclusions:The twinning rate observed in Chennai in the present study is interestingly very high, compared to the overall twinning rate reported in the past in the state of Tamilnadu. The Wienberg’s Differential method for zygosity determination is again found to be questionable. The zygosity proportion, maternal age and parity relations are not very different from previously available data.

The influence of environmental and genetic factors on the development of psychopathy: A systematic review

The aim of this review is to understand what is known about the genetic and environmental influences on the development of psychopathy. Psychopathy is considered a personality structure in which affective, interpersonal, and behavioral deficits are evidenced. Both genetic and environmental effects contribute to the development of this personality structure. In this systematic review, documents from several databases were analyzed, following the PRISMA guidelines. To avoid publication and source selection bias, these database searches were supplemented by an additional manual search. A total of 159 studies, published between 1981 and 2021, were identified from all databases and search methods. The studies' abstracts were available, and 37 studies were selected. In addition, two studies were included from the manual research. Thus, a total of 39 studies were selected for review. The results of the studies suggest that the monoamine oxidase genotype (MAOA), dopamine transporter gene (DAT1), dopamine receptor D5 (DRD5) and serotonin transporter gene (5HTTLPR) are frequently associated with antisocial behavior, although with different behavioral manifestations between men and women, and that the dopamine receptor gene alleles (DRD2 and DRD4) are good delinquency predictors. In addition, genetic and non-shared environmental factors are those with the most influence on antisocial behavior, specifically psychopathy, with the correlation values of monozygotic twins being higher than those of dizygotic twins, thus demonstrating the importance of genes. It was concluded that genetic factors influence the development of both antisocial behavior and psychopathy. However, environmental factors often contribute to the exacerbation of genetic factors.

Exploration of Twin Separation and Adult Experiences: A Qualitative Study

Many researchers have studied the long-term impact of nontwin sibling separation in foster care, but little is known about the separation of twins. In this study, we examined how one specific set of adult fraternal twin sisters interpreted their personal experiences of separation from each other while in foster care and whether this experience affected their interpersonal relationships. The researchers relied on the theoretical foundations of attachment theory to support the use of existing literature and to integrate the research findings into current child welfare practice for human services professionals. Through personal interviews, each twin was asked to recall experiences from foster care and comment on the effects of being separated from their twin. Thematic analysis of the interview data and observations of the interview process helped to identify four themes: forming successful attachments, mental health issues, trauma history, and number and type of placements experienced. Implications for human services professionals working in social services agencies with youth in foster care are also discussed.

Zygosity Test of Twin Pairs Using 26 STR Loci in the Indonesian Population

Background: Twin research can play an important role in understanding the interplay between genes and environment. Classifying twins as monozygotic (identical) or dizygotic (fraternal) is an essential first step in conducting research that will yield valid and replicable findings. Identical twins (theoretically) share 100% of their genes, while fraternal twins share, on average, 50% of their genes.1 This study aims to determine zygosity in 12 twins with Non-Syndromic Cleft Lip and Palate (NSCLP) discordant, concordant, and non-NSCLP.Material and Methods: Blood samples from 12 twin pairs, which include of 8 twins Non-syndromic Cleft Lip and Palate (NSCLP) discordant, 2 twins NSCLP concordant, and 2 twins non-cleft (normal). DNA extraction was using Promega Kit and quantified was using Nano drops. DNA amplification was by PCR with 26 loci, which was packaged in Powerplex Fusion 6C Kit. PCR products were sequenced using ABI3500 and the visualization can be seen using Genemapper TM ID-X 1.6 software.Results: The results show that each pair of 11 twins have a similar alleles in 26 STR loci, which means they are monozygotic twins. Only 1 twin has a different alleles in 10 STR loci, which means they are dizygote.Conclusion: Zygosity tests on MZ twins using STR loci has high similarity and sensitivity. This test would be more accurate by analyzing a higher number of STR loci.

Twin quark dark matter from cogenesis

We extend the fraternal twin Higgs scenario to include a novel dark matter candidate as well as a mechanism for generating a matter/antimatter asymmetry in both sectors. A spontaneous breaking of twin color results in quark degrees of freedom that are singlets under the residual twin color group. These twin-color-singlet quarks, along with a subdominant component of twin leptons, constitute the asymmetric dark matter. The asymmetry between matter in antimatter in both sectors is co-generated from the decay of singlet fermions that provide an additional portal between the visible and twin sectors. We discuss the phenomenological aspects of this model, evaluating constraints on the parameter space and highlighting promising discovery channels in future experiments. We briefly discuss how the discovery of signals in multiple experiments may help establish the connection between the mechanisms that address the naturalness, dark matter and matter/antimatter asymmetry puzzles.

Familial risk and heritability of intellectual disability: a population-based cohort study in Sweden.

Intellectual disability (ID) aggregates in families, but factors affecting individual risk and heritability estimates remain unknown. A population-based family cohort study of 4,165,785 individuals born 1973-2013 in Sweden, including 37,787 ID individuals and their relatives. The relative risks (RR) of ID with 95% confidence intervals (95% CI) were obtained from stratified Cox proportional-hazards models. Relatives of ID individuals were compared to relatives of unaffected individuals. Structural equationmodeling was used to estimate heritability. Relatives of ID individuals were at increased risk of ID compared to individuals with unaffected relatives. The RR of ID among relatives increased proportionally to the degree of genetic relatedness with ID probands; 256.70(95% CI 161.30-408.53) for monozygotic twins, 16.47(13.32-20.38) for parents, 14.88(12.19-18.16) for children, 7.04(4.67-10.61) for dizygotic twins, 8.38(7.97-8.83) for full siblings, 4.56(4.02-5.16) for maternal, 2.90(2.49-3.37) for paternal half-siblings, 3.03(2.61-3.50) for nephews/nieces, 2.84(2.45-3.29) for uncles/aunts, and 2.04(1.91-2.20) for cousins. Lower RRs were observed for siblings of probands with chromosomal abnormalities (RR 5.53, 4.74-6.46) and more severe ID (mild RR 9.15, 8.55-9.78, moderate RR 8.13, 7.28-9.08, severe RR 6.80, 5.74-8.07, and profound RR 5.88, 4.52-7.65). Male sex of relative and maternal line of relationship with proband was related to higher risk (RR 1.33, 1.25-1.41 for brothers vs. sisters and RR 1.49, 1.34-1.68 for maternal vs. paternal half-siblings). ID was substantially heritable with 0.95(95% CI 0.93-0.98) of the variance in liability attributed to genetic influences. The risk estimates will benefit researchers, clinicians, families in understanding the risk of ID in the family and the whole population. The higher risk of ID related to male sex and maternal linage will be of value for planning and interpreting etiological studies in ID.

The heritability of amyloid burden in older adults: the Older Australian Twins Study

ObjectiveTo determine the proportional genetic contribution to the variability of cerebral β-amyloid load in older adults using the classic twin design.MethodsParticipants (n=206) comprising 61 monozygotic (MZ) twin pairs (68 (55.74%)...

Discrepancies in Objective and Subjective Fine Motor Abilities in Octogenarians

Older individuals may have discrepancies between self-reported and performance-based abilities on activities of daily living (ADL). We examined objective and self-reported fine motor abilities (FMA). FMA are required for many ADLs, but are examined less frequently than gross-motor tasks in this population. We used two waves of the population-based OCTO-Twin study including mono-/dizygotic Swedish twins, aged 80+. One twin was randomly selected for analyses (baseline N=262; wave 2 N=198; Meanage =83.27; SDage=2.90; 66.4% female). Participants self-reported their ability to manipulate things with hands (cannot do, some problem, no problem) and completed a timed FMA assessment including five everyday tasks (e.g. inserting a key in a lock). Slow performance was coded as 1+ SD from the mean (=80+ seconds). At baseline, 65.8% of slow performers reported ‘no problems’ with hand manipulation. Over two waves (two years), a two-factor ANOVA (including slowness-by-perception interaction) supported a significant difference in total motor task performance between slow performers reporting ‘no problems’ and fast performers reporting ‘no problems’, for both rate of change (diff = -26 seconds, p<.0001) and wave 2 level (diff = 50 seconds, p < .0001). 82% of slow performers at wave 2 reported ‘no problems’, which is surprising given that they had become even slower over the past two years. Findings suggest that objective FMA measures are needed, as self-report is inaccurate and not prognostic. Future work will examine if discrepancies in performance/perceived FMA predict poorer outcomes, and/or if reporting ‘no problems’ despite slower performance is protective against cognitive adaptation to slowing.

Twin Similarity for Neighborhood, Geographic Mobility, and Health Outcomes in Late Adulthood

Socioeconomic status (SES) is one of the most robust predictors of health. The source of SES-health associations is heavily debated; one approach is investigating neighborhood-level environmental characteristics. Challenges include selection effects and the possibility of reverse causation: people choose their neighborhoods. Longitudinal twin research can overcome these issues by assessing location choice over time as well as twin similarity; however, few existing twin studies have incorporated neighborhood-level data, and none of those focus on aging. Using longitudinal data from the Swedish Adoption/Twin Study of Aging, the current study examined the impact of location at various points in life. Location at birth and in 1993 were available for 972 participants. Birth years ranged from 1926 to 1948; mean age in 1993 was 54.55 (range = 35-67). Thirty-nine percent of the sample had moved to a different county between birth and midlife: individuals who moved had significantly higher parental SES and had achieved significantly higher education. Moreover, identical twin concordance for geographic mobility (77%) was significantly higher than fraternal twin concordance (65%), indicating a modest but significant genetic contribution. Geographic mobility did not impact identical twin similarity on a functional aging factor (corrected for age and education), but fraternal twins concordant for mobility were more similar than discordant twins, suggesting genetic contributions to mobility may also impact health. Ongoing retrieval of location information for twins born 1900-1925 and geocoding of location information available at 9 waves of data collection will allow for expanded investigation of the SES-health relationship at the neighborhood level.

Random Developmental Variation of Human Phenotypic Traits, as Estimated by Fluctuating Asymmetry and Twin Studies

Random developmental variation, or developmental noise, contributes to total phenotypic variation in the human species. Despite exhortations to examine it, especially with respect to human behavior and intelligence, there has been little research specifically devoted to doing so. Random developmental variation can be estimated in studies of fluctuating asymmetry and comparisons of monozygotic and dizygotic twins. Estimation of random developmental variation requires that both genotype and environment be held constant. In a small sample of bilaterally symmetrical traits (dermatoglyphic ridge counts, digit lengths, ear lengths and widths), I show how the random developmental component can be estimated. In these traits, the percentage of total phenotypic variation attributable to developmental noise ranges from 3 percent to more than 25 percent. Moreover, for dermatoglyphic ridge counts, fluctuating asymmetry and twin comparisons give essentially the same estimates.

The aetiology of educational attainment: A nuclear twin family study into the genetic and environmental influences on school leaving certificates.

Educational attainment is connected to many important life outcomes, and the previous research has already focused on identifying its genetic and environmental components. However, most of these studies used twin data only and did not incorporate information from other family members. Twin studies typically decompose the phenotypic variance into genetic, shared, and unique environment components. In this study design, the shared environment component encompasses the influence of parents and the shared environments of twins and siblings independent of parents (e.g., teachers, schools, and peers). The classical twin design (CTD) conflates these influences as part of the shared environment. This shortcoming can be overcome using the nuclear twin family design (NTFD), which enables separation of the parental and shared twin/sibling environmental components. The aim of this study was to broaden the understanding of the aetiology of educational attainment using the nuclear twin family design to provide a detailed account of the genetic and environmental effects on the type of school leaving certificate. The data of 1,048 monozygotic and 916 dizygotic same-sex twins, their biological parents, and non-twin full biological siblings of the German project TwinLife were used in the nuclear twin family design. Structural equationmodelling (SEM) techniques were used to analyse the variance-covariance patterns of the ordinal outcome variable. Genetic influences were found to make up around 60% of variance, whilst environmental influences shared by all siblings, educational influences shared by the twins only, and non-shared environmental influences explained the remaining variance in equal amounts. Environmental transmission from parent to offspring was found to be negligible. Through its advanced design, our study extends the previous work enabling more detailed and robust estimations of sources of variance and contributes to a better understanding of the complex aetiology of educational attainment.

Dental age estimation using three different methods in monozygotic and dizygotic twins

ABSTRACT Dental development, one of the most reliable indicators of chronological age (CA), has been believed to be fundamentally influenced by genetics rather than environmental factors. The study aims (i) to compare dental ages (DAs) in monozygotic (MZ) and dizygotic (DZ) twins using three different DA methods and determining the most appropriate method, and (ii) to determine the possible effects of genetics on DA by evaluating the differences in the estimated DAs of MZ and DZ twins. The study sample consisted of 171 twin pairs (47 monozygotic, 124 dizygotic) between the ages of 5.0 and 12.9. In order to estimate DA, Demirjian, Willems and Nolla methods were used. The mean CA of group was 8.42 (2.05) years. The Demirjian, Willems and Nolla methods overestimated the DAs by 0.69, 0.60 and 0.56 years, respectively. The estimated DAs in age groups were similar, and differences were not statistically significant for intrapair DZ and MZ twins. As a result, it was not correct to state that any method was more appropriate and better than others for studies of twins. All methods’ standards were not suitable for any age groups of MZ and DZ twins, except for twins aged 12–12.9 years. Country-wide samples are needed to gather enough data to create valuable results and to establish the applicability of methods used.

P.0872 The association between childhood trauma discordance and suicide ideation among monozygotic and dizygotic twins

P.0872 The association between childhood trauma discordance and suicide ideation among monozygotic and dizygotic twins

Three Patterns of Inheritance of Quantitative Dermatoglyphic Traits: Kosovo Albanian Twin Study.

Dermatoglyphs are epidermal ridge configurations on the fingers, palms and soles that are formed during fetal development, and therefore only the intrauterine environment can have any influence on their formation. This study aims at investigating the genetic and environmental contribution in determining quantitative dermatoglyphic traits in 32 monozygotic (MZ) and 35 dizygotic (DZ) same-sex twins from the Albanian population of Kosovo. All genetic analyses were run in the statistical program Mx. After assumptions testing, based on the pattern of MZ-DZ correlations, univariate models were fitted to the data in order to estimate additive genetic (A), common (C) and individual (E) environmental influences for all variables. The exception was the atd-angle for which a model with nonadditive genetic (D) influences was tested, since DZ correlations were less than half of MZ correlations. Goodness of fit of the full ACE or ADE model was compared to the saturated model. The fit of nested models (AE, CE, DE or E) was compared to the full models (ACE or ADE). Our results indicate that additive genetic component strongly contributes to individual differences in finger ridge counts (49-81%), and weakly (0-50%) on the formation of the palmar ridge counts between the palmar triradii a, b, c, and d. The specific pattern found for the atd-angle implies the impact of a nonadditive genetic component, possibly the effect of a major gene. Further, more powered studies are needed to confirm this pattern, especially for resolving the issue of the huge difference in MZ and DZ twin similarity for the atd-angle palmar trait.

Conducting Clinical Trials in Twin Populations: A Review of Design, Analysis, Recruitment and Ethical Issues for Twin-Only Trials.

Although twins often participate in medical research, few clinical trials are conducted entirely in twin populations. The purpose of this review is to demonstrate the substantial benefits and address the key challenges of conducting clinical trials in twin populations, or 'twin-only trials'. We consider the unique design, analysis, recruitment and ethical issues that arise in such trials. In particular, we describe the different approaches available for randomizing twin pairs, highlight the similarity or correlation that exists between outcomes of twins, and discuss the impact of this correlation on sample size calculations and statistical analysis methods for estimating treatment effects. We also consider the role of both monozygotic and dizygotic twins for studying variation in outcomes, the factors that may affect recruitment of twins, and the ethics of conducting trials entirely in twin populations. The advantages and disadvantages of conducting twin-only trials are also discussed. Finally, we recommend that twin-only trials should be considered more often.

Mysteries of Monozygosity: Theories and Breakthroughs/Twin Research: Rare Case of Lost Twins; Developing a National Twin Registry; Twins' Language and Gesture Delays; DNA Testing for Vanishing Twins/Media Reports: Identical Twins Discordant for COVID Vaccination; World's Oldest Identical Twins; Olympic Athlete Stand-in; Fraternal Twin Football Players.

The processes that give rise to monozygotic (MZ) twins remain elusive. This article describes various theories of MZ twinning that have been examined over the years, although they continue to be speculative. It has also been impossible to know if a singleton began life as an MZ twin; however, a critical technological breakthrough can now reveal this important birth history information with a high degree of certainty. The section that follows presents reviews of current research regarding rare twin loss, development of a twin registry, twins' communicative delays and DNA testing for vanishing twins. The article concludes with a survey of newsworthy twins, namely identical twins discordant for COVID vaccination, the world's oldest identical twins, an Olympic athletic stand-in and fraternal twin football players.

Comprehensive Management of Congenital Cataract in Dizygotic Twin Babies

Introduction: One of the leading causes of infant blindness is cataract. The prevalence of congenital cataract has been estimated in the range between 1 and 15 per 10.000 children globally. Congenital cataract in twin babies is a rare case. This case will report the outcome of comprehensive management of congenital cataract in dizygotic twin babies. Case presentation: Eight months old dizygotic twin babies came to our clinic with the primary complaint of whitish appearance in the pupil of both eyes since birth. They were born aterm with cesarean delivery. The birth weight was 2.700 g and 3.100 g respectively. They were the fourth and fifth children in the family. There was no family history of congenital cataract. The visual acuity of both eyes was positive response to light stimuli. The cataract was bilateral and dense on both babies. Fundus reflex and TORCH examinations were negative. Ultrasonography (USG) of the retina was normal on both babies. Conclusions: Isolated congenital cataract in twin babies is an unusual condition that should be treated comprehensively. Congenital cataract may cause deprivation amblyopia, refractive amblyopia, and permanent vision impairment. Early diagnosis and quick treatment, such as surgical timing and visual rehabilitation, are critical to perform successful management. Comprehensive care is required to monitor the visual result of cataract surgery.