-
BMC Oral Health Oct 2020DNA base identification is a proper and high specificity method. However, identification could be challenged in a situation where there is no database or the DNA...
BACKGROUND
DNA base identification is a proper and high specificity method. However, identification could be challenged in a situation where there is no database or the DNA sequence is almost identical, as in the case of monozygotic (MZ) twins. The aim of this study was to introduce a novel forensic method for distinguishing between almost identical MZ twins by means of an intraoral scanner using the 3D digital pattern of the human palate.
METHODS
The palatal area of 64 MZ twins and 33 same-sex dizygotic (DZ) twins (DZSS) and seven opposite-sex dizygotic twins (DZOS) were scanned three times with an intraoral scanner. From the scanned data, an STL file was created and exported into the GOM Inspect® inspection software. All scans within a twin pair were superimposed on each other. The average deviation between scans of the same subject (intra-subject deviation, ISD) and between scans of the two siblings within a twin pair (intra-twin deviation, ITD) was measured. One-sided tolerance interval covering 99% of the population with 99% confidence was calculated for the ISD (upper limit) and the ITD (lower limit).
RESULTS
The mean ISD of the palatal scan was 35.3 μm ± 0.78 μm. The calculated upper tolerance limit was 95 μm. The mean ITD of MZ twins (406 μm ± 15 μm) was significantly (p < 0.001) higher than the ISD, and it was significantly lower than the ITD of DZSS twins (594 μm ± 53 μm, p < 0.01) and the ITD of DZOS twins (853 μm ± 202 μm, p < 0.05).
CONCLUSION
The reproducibility of palatal intraoral scans proved to be excellent. The morphology of the palate shows differences between members of MZ twins despite their almost identical DNA, indicating that this method could be useful in forensic odontology.
Topics: Humans; Palate; Reproducibility of Results; Software; Twins, Dizygotic; Twins, Monozygotic
PubMed: 33008463
DOI: 10.1186/s12903-020-01261-w -
Behavior Genetics Mar 2017We compared the nature of the sibling relationship in dyads of varying genetic relatedness, employing a behavioural genetic design to estimate the contribution that...
We compared the nature of the sibling relationship in dyads of varying genetic relatedness, employing a behavioural genetic design to estimate the contribution that genes and the environment have on this familial bond. Two samples were used-the Sisters and Brothers Study consisted of 173 families with two target non-twin children (mean ages = 7.42 and 5.22 years respectively); and the Twins, Family and Behaviour study included 234 families with two target twin children (mean age = 4.70 years). Mothers and fathers reported on their children's relationship with each other, via a postal questionnaire (the Sisters and Brothers Study) or a telephone interview (the Twins, Family and Behaviour study). Contrary to expectations, no mean level differences emerged when monozygotic twin pairs, dizygotic twin pairs, and non-twin pairs were compared on their sibling relationship quality. Behavioural genetic analyses also revealed that the sibling bond was modestly to moderately influenced by the genetic propensities of the children within the dyad, and moderately to substantially influenced by the shared environment common to both siblings. In addition, for sibling negativity, we found evidence of twin-specific environmental influence-dizygotic twins showed more reciprocity than did non-twins. Our findings have repercussions for the broader application of results from future twin-based investigations.
Topics: Adult; Child; Child, Preschool; Environment; Fathers; Female; Genetics, Behavioral; Humans; Male; Mothers; Siblings; Social Behavior; Social Environment; Surveys and Questionnaires; Twins; Twins, Dizygotic; Twins, Monozygotic
PubMed: 27796609
DOI: 10.1007/s10519-016-9825-z -
PloS One 2011Earlier studies have shown variation among experimental attempts to establish whether human monozygotic twins that are genetically identical also have identical...
Earlier studies have shown variation among experimental attempts to establish whether human monozygotic twins that are genetically identical also have identical individual scents. In none of the cases were the dogs able to distinguish all the individual scents of monozygotic twins living in the same environment if the scents were presented to them separately. Ten specially trained police German Shepherd dogs of three Czech Republic Police Regional Headquarters were used for scent identification in our study. The dogs were supposed to match scents of two monozygotic pairs (5 and 7 years old) and two dizygotic twin pairs (8 and 13 years old). Scents were collected on cotton squares stored in glass jars. Dog handlers were blind to the experiment details. In each trial (line-up), one scent was used as a starting scent and the dog was then sent to determine if any of the 7 presented glass jars contained a matching scent. Scents of children of similar ages were used as distractors. In the matching procedure, the dogs matched correctly the scent of one twin with the other, as well as two scents collected from every single identical and non-identical twin to prove their efficacy and likewise, the presence of the matching twin scent in any given glass jar. All dogs in all trials distinguished correctly the scents of identical as well as non-identical twins. All dogs similarly matched positively two scents collected from the same individuals. Our findings indicated that specially trained German Shepherd dogs are able to distinguish individual scents of identical twins despite the fact that they live in the same environment, eat the same food and even if the scents are not presented to them simultaneously.
Topics: Animals; Dogs; Humans; Odorants; Smell; Twins, Monozygotic
PubMed: 21698282
DOI: 10.1371/journal.pone.0020704 -
BMC Genomics Jul 2014Crohn's disease (CD) is an inflammatory bowel disease caused by genetic and environmental factors. More than 160 susceptibility loci have been identified for IBD, yet a...
BACKGROUND
Crohn's disease (CD) is an inflammatory bowel disease caused by genetic and environmental factors. More than 160 susceptibility loci have been identified for IBD, yet a large part of the genetic variance remains unexplained. Recent studies have demonstrated genetic differences between monozygotic twins, who were long thought to be genetically completely identical.
RESULTS
We aimed to test if somatic mutations play a role in CD etiology by sequencing the genomes and exomes of directly affected tissue from the bowel and blood samples of one and the blood-derived exomes of two further monozygotic discordant twin pairs. Our goal was the identification of mutations present only in the affected twins, pointing to novel candidates for CD susceptibility loci. We present a thorough genetic characterization of the sequenced individuals but detected no consistent differences within the twin pairs. An estimate of the CD susceptibility based on known CD loci however hinted at a higher mutational load in all three twin pairs compared to 1,920 healthy individuals.
CONCLUSION
Somatic mosaicism does not seem to play a role in the discordance of monozygotic CD twins. Our study constitutes the first to perform whole genome sequencing for CD twins and therefore provides a valuable reference dataset for future studies. We present an example framework for mosaicism detection and point to the challenges in these types of analyses.
Topics: Adult; Base Sequence; Crohn Disease; DNA Copy Number Variations; Exome; Female; Genetic Predisposition to Disease; Genome, Human; Genome-Wide Association Study; Humans; Middle Aged; Molecular Sequence Data; Mutation; Polymorphism, Single Nucleotide; Sequence Analysis, DNA; Twins, Monozygotic
PubMed: 24996980
DOI: 10.1186/1471-2164-15-564 -
Perspectives on Psychological Science :... Nov 2023What are the major sources of worldwide variability in subjective well-being (SWB)? Twin and family studies of SWB have found substantial heritability and strong effects...
What are the major sources of worldwide variability in subjective well-being (SWB)? Twin and family studies of SWB have found substantial heritability and strong effects from unique environments but virtually no effects from shared environments. However, extant findings are not necessarily valid at the global level. Prior studies have examined within-countries variability but did not take into account mean differences across nations. In this article, we aim to estimate the effects of genetic factors, individual environmental exposures, and shared environments for the global population. We combine a set of knowns from national well-being studies (means and standard deviations) and behavioral-genetic studies (heritability) to model a scenario of twin studies across 157 countries. For each country, we simulate data for a set of twin pairs and pool the data into a global sample. We find a worldwide heritability of 31% to 32% for SWB. Individual environmental factors explain 46% to 52% of the variance (including measurement error), and shared environments account for 16% to 23% of the global variance in SWB. Worldwide, well-being is somewhat less heritable than within nations. In contrast to previous within-countries studies, we find a notable effect of shared environments. This effect is not limited to within families but operates at a national level.
Topics: Humans; Twins, Dizygotic; Twins, Monozygotic; Environmental Exposure; Gene-Environment Interaction; Genetics
PubMed: 37384562
DOI: 10.1177/17456916231178716 -
Journal of the American Academy of... Feb 2019Psychotic experiences (PE) are dimensional phenomena in the general population that resemble psychotic symptoms, such as paranoia and hallucinations. This is the first...
OBJECTIVE
Psychotic experiences (PE) are dimensional phenomena in the general population that resemble psychotic symptoms, such as paranoia and hallucinations. This is the first twin study to explore the degree to which tobacco use and PE share genetic or environmental influences. Previous studies on the association between adolescent tobacco use and PE have not considered PE dimensionally, included negative symptoms, or accounted for confounding by sleep disturbance and stressful life events.
METHOD
An unselected adolescent twin sample (N = 3,787 pairs; mean age = 16.16 years) reported on PE (paranoia, hallucinations, cognitive disorganization, grandiosity, and anhedonia) and regularity of tobacco use. Parents rated the twins' negative symptoms. Regression analyses were conducted while adjusted for sociodemographic characteristics, prenatal maternal smoking, cannabis use, sleep disturbance, and stressful life events. Bivariate twin modeling was used to estimate the degree of genetic and common and unique environmental influences shared between tobacco use and PE.
RESULTS
Regular smokers were significantly more likely to experience paranoia, hallucinations, cognitive disorganization, and negative symptoms (β = 0.17-0.34), but not grandiosity or anhedonia, than nonsmokers, after adjustment for confounders. Paranoia, hallucinations, and cognitive disorganization correlated ≥0.15 with tobacco use (r = 0.15-0.21, all p < .001). Significant genetic correlations (r=0.37-0.45) were found. Genetic influences accounted for most of the association between tobacco use and paranoia (84%) and cognitive disorganization (81%). Familial influences accounted for 80% of the association between tobacco use and hallucinations.
CONCLUSION
Tobacco use and PE during adolescence were associated after adjustment for confounders. They appear to co-occur largely because of shared genetic influences.
Topics: Adolescent; Female; Genetic Predisposition to Disease; Hallucinations; Humans; Male; Psychotic Disorders; Regression Analysis; Tobacco Use; Twins, Dizygotic; Twins, Monozygotic; United Kingdom
PubMed: 30738553
DOI: 10.1016/j.jaac.2018.06.037 -
Cerebral Cortex (New York, N.Y. : 1991) Mar 2019Females might possess protective mechanisms regarding autism spectrum disorder (ASD) and require a higher detrimental load, including structural brain alterations,...
Females might possess protective mechanisms regarding autism spectrum disorder (ASD) and require a higher detrimental load, including structural brain alterations, before developing clinically relevant levels of autistic traits. This study examines sex differences in structural brain morphology in autism and autistic traits using a within-twin pair approach. Twin design inherently controls for shared confounders and enables the study of gene-independent neuroanatomical variation. N = 148 twins (62 females) from 49 monozygotic and 25 dizygotic same-sex pairs were included. Participants were distributed along the whole continuum of autism including twin pairs discordant and concordant for clinical ASD. Regional brain volume, surface area, and cortical thickness were computed. Within-twin pair increases in autistic traits were related to decreases in cortical volume and surface area of temporal and frontal regions specifically in female twin pairs, in particular regions involved in social communication, while only two regions were associated with autistic traits in males. The same pattern was detected in the monozygotic twin pairs only. Thus, non-shared environmental factors seem to impact female more than male cerebral architecture associated with autistic traits. Our results are in line with the hypothesis of a female protective effect in autism and highlights the need to study ASD in females separately from males.
Topics: Adolescent; Adult; Autism Spectrum Disorder; Brain; Child; Female; Gene-Environment Interaction; Genetic Predisposition to Disease; Humans; Male; Sex Characteristics; Twins, Dizygotic; Twins, Monozygotic; Young Adult
PubMed: 30566633
DOI: 10.1093/cercor/bhy303 -
Genes Feb 2022The familial occurrence of childhood cancers has been proven for a long time. Wilms' tumors often do not have a clear germline genetic cause. However, approximately 2%... (Review)
Review
The familial occurrence of childhood cancers has been proven for a long time. Wilms' tumors often do not have a clear germline genetic cause. However, approximately 2% of all nephroblastoma cases are familial. Descriptions of twins with the same cancer are extremely rare, so our aim was to present the background of the available literature of the occurrence of Wilms' tumor in a pair of monozygotic twin girls with detailed clinical, histological, and molecular analysis. Two twins were born of unrelated Caucasian parents. Family history revealed no known chronic diseases or malformations. At the age of 3.5 years, the first twin was admitted to the emergency department due to hematuria and abdominal pain. Ultrasound examination revealed an enlarged right kidney, 12.8 cm, with a mass in the upper pole measuring 56 × 69 × 78 mm. The second girl was referred for an abdominal ultrasound, which revealed a right kidney measuring 8.6 cm with a central mass measuring 54 × 45 × 41 mm. Both children underwent surgical resection, and the histopathological result showed a mixed form of nephroblastoma, predominantly epithelioid with residual blastemal compartment. Detailed clinical, histological, cytogenetic, and molecular analyses were performed on both sisters. It was also decided to identify environmental factors. Information was obtained that the girls' parents run a farm and regularly use pesticides and chemical rodenticides. Based on our observations and the available literature, Wilms tumor in monozygotic twins may be present. Both genetic and environmental factors may be involved in the development of tumors. After excluding methylation abnormalities and mutations in the genes studied, we questioned whether the onset of Wilms tumor in both sisters could be the result of exposure of the twins' parents to pesticides.
Topics: Child; Child, Preschool; Cytogenetic Analysis; Female; Humans; Kidney Neoplasms; Pesticides; Twins, Monozygotic; Wilms Tumor
PubMed: 35205416
DOI: 10.3390/genes13020372 -
Journal of Psychiatry & Neuroscience :... May 1994This paper reviews key studies that have addressed genetic and neurobiological aspects in attention deficit hyperactive disorder. Genetic studies can be divided into... (Review)
Review
This paper reviews key studies that have addressed genetic and neurobiological aspects in attention deficit hyperactive disorder. Genetic studies can be divided into three distinct types: twin, adoption, and family studies. Evidence for a particular mode of inheritance and the possible specific genetic abnormalities are also explored. There is strong evidence of genetic involvement in this condition, although a clear-cut mode of inheritance and specific genetic abnormalities are yet to be determined. Neurobiological aspects such as the neuroanatomical and neurochemical evidence of various neurotransmitter system involvement is explored. Frontal lobe and dopamine and norepinephrine neurotransmitter systems appear to be involved in attention deficit hyperactive disorder.
Topics: Adoption; Attention Deficit Disorder with Hyperactivity; Child; Comorbidity; Diseases in Twins; Humans; Models, Genetic; Risk Factors; Social Environment; Synaptic Transmission; Twins, Dizygotic; Twins, Monozygotic
PubMed: 8031743
DOI: No ID Found -
Nicotine & Tobacco Research : Official... Jun 2018Classical twin studies show that smoking is heritable. To determine if shared family environment plays a role in addition to genetic factors, and if they interact...
INTRODUCTION
Classical twin studies show that smoking is heritable. To determine if shared family environment plays a role in addition to genetic factors, and if they interact (G×E), we use a children-of-twins design. In a second sample, we measure genetic influence with polygenic risk scores (PRS) and environmental influence with a question on exposure to smoking during childhood.
METHODS
Data on smoking initiation were available for 723 children of 712 twins from the Netherlands Twin Register (64.9% female, median birth year 1985). Children were grouped in ascending order of risk, based on smoking status and zygosity of their twin-parent and his/her co-twin: never smoking twin-parent with a never smoking co-twin; never smoking twin-parent with a smoking dizygotic co-twin; never smoking twin-parent with a smoking monozygotic co-twin; and smoking twin-parent with a smoking or never smoking co-twin. For 4072 participants from the Netherlands Twin Register (67.3% female, median birth year 1973), PRS for smoking were computed and smoking initiation, smoking heaviness, and exposure to smoking during childhood were available.
RESULTS
Patterns of smoking initiation in the four group children-of-twins design suggested shared familial influences in addition to genetic factors. PRS for ever smoking were associated with smoking initiation in all individuals. PRS for smoking heaviness were associated with smoking heaviness in individuals exposed to smoking during childhood, but not in non-exposed individuals.
CONCLUSIONS
Shared family environment influences smoking, over and above genetic factors. Genetic risk of smoking heaviness was only important for individuals exposed to smoking during childhood, versus those not exposed (G×E).
IMPLICATIONS
This study adds to the very few existing children-of-twins (CoT) studies on smoking and combines a CoT design with a second research design that utilizes polygenic risk scores and data on exposure to smoking during childhood. The results show that shared family environment affects smoking behavior over and above genetic factors. There was also evidence for gene-environment interaction (G×E) such that genetic risk of heavy versus light smoking was only important for individuals who were also exposed to (second-hand) smoking during childhood. Together, these findings give additional incentive to recommending parents not to expose their children to cigarette smoking.
Topics: Adolescent; Adult; Child; Cohort Studies; Female; Gene-Environment Interaction; Humans; Male; Netherlands; Parents; Registries; Risk Factors; Smoking; Surveys and Questionnaires; Twins, Dizygotic; Twins, Monozygotic
PubMed: 28575460
DOI: 10.1093/ntr/ntx121