Search results for "Dizygotic"
showing 10 items of 77 documents
Sport disciplines, types of sports, and waist circumference in young adulthood – a population-based twin study
2017
Purpose: The benefits of physical activity (PA) in preventing abdominal obesity are well recognized, but the role of different sport disciplines remains open. We aimed, therefore, to investigate how participation in different sport disciplines, and the number and types of sports engaged in are associated with waist circumference (WC) in young adulthood. Methods: This population-based cohort study comprised 4027 Finnish twin individuals (1874 men), with a mean age of 34 y (32-37), who answered a survey, including self-measured WC. We extracted the number and identified the types (aerobic, power, and mixed) of the different sport disciplines respondents reported participating in. Results: The…
Decreased prevalence of left-handedness among females with male co-twins: evidence suggesting prenatal testosterone transfer in humans?
2009
Studies of singletons suggest that right-handed individuals may have higher levels of testosterone than do left-handed individuals. Prenatal testosterone levels are hypothesised to be especially related to handedness formation. In humans, female members from opposite-sex twin pairs may experience elevated level of prenatal exposure to testosterone in their intra-uterine environment shared with a male. We tested for differences in rates of left-handedness/right-handedness in female twins from same-sex and opposite-sex twin pairs. Our sample consisted of 4736 subjects, about 70% of all Finnish twins born in 1983–1987, with information on measured pregnancy and birth related factors. Circulati…
DSM-IV Combined Type ADHD Shows Familial Association With Sibling Trait Scores
2008
Contains fulltext : 69060.pdf (Publisher’s version ) (Closed access) Attention deficit hyperactivity disorder (ADHD) is a discrete clinical syndrome characterized by the triad of inattention, hyperactivity, and impulsivity in the context of marked impairments. Molecular genetic studies have been successful in identifying genetic variants associated with ADHD, particularly with DSM-IV inattentive and combined subtypes. Quantitative trait locus (QTL) approaches to linkage and association mapping have yet to be widely used in ADHD research, although twin studies investigating individual differences suggest that genetic liability for ADHD is continuously distributed throughout the population, u…
The heritability of depressive symptoms: multiple informants and multiple measures
2002
Background: Earlier research suggests large rater differences in heritability estimates of children's depressive symptoms in the context of significant age and sex-limitation effects. Methods: With data from an ongoing, population-based twin-family study, we estimated genetic and environmental influences on children's depression with models allowing for sex-specific effects. Our assessments of twins included self-reports and ratings made by their classmate peers, their parents and their teachers, allowing estimates of genetic and environmental effects with data from different informants. Model-fitting used maximum likelihood estimation of log-transformed data from a sample of 1,366 11- and …
Genetic and Environmental Influences Underlying Externalizing Behaviors, Cigarette Smoking and Illicit Drug Use Across Adolescence
2012
We investigated genetic and environmental influences common to adolescent externalizing behavior (at age 12), smoking (at age 14) and initiation of drug use (at age 17) using the FinnTwin12 cohort data. Multivariate Cholesky models were fit to data from 737 monozygotic and 722 dizygotic twin pairs. Heritability of externalizing behavior was 56%, that of smoking initiation/amount 20/32%, and initiation of drug use 27%. In the best-fitting model common environmental influences explained most of the covariance between externalizing behavior and smoking initiation (69%) and amount (77%). Covariance between smoking initiation/amount and drug use was due to additive genetic (42/22%) and common en…
Unpredicted ovulations and conceptions during early pregnancy: an explanatory mechanism of human superfetation
2012
In this bioessay, a literature review on human superfetation was performed in order to find epidemiological variables associated with this phenomenon. Thereafter, an explanatory mechanism of superfetation compatible with the endocrinological, histological and physiological changes undergone by women during early pregnancy is proposed. Superfetation can be defined as the ovulation, fertilisation and implantation of a second or additional embryo(s) during pregnancy. The literature review evidences a small discordance in gestational age between dizygotic twins in humans (range: 2–4 weeks; mean ± s.e.m.: 3.3 ± 0.3 weeks). This difference is compatible with a luteal out-of-phase (LOOP; i.e. atyp…
Mirror imaging of impacted and supernumerary teeth in dizygotic twins: A case report
2015
Background: Mesiodens is the most common type of supernumerary tooth found in the premaxilla. It might be discovered during the clinical examination as a casual finding on a radiograph or as the cause of an unerupted maxillary central incisor. The genetic transmission of supernumerary and impacted teeth is poorly understood. Mirror imaging in twins has been reported frequently in relation to several unilateral dental anomalies including mesiodens. This phenomenon is the appearance of an asymmetrical feature or anomaly occurring on the right side of one twin but on the left side of the other twin. The event of mesiodens mirror imaging in monozygotic twins has been described in literature. Re…
Muscle Cross-Sectional Area and Structural Bone Strength Share Genetic and Environmental Effects in Older Women
2009
The purpose of this study was to estimate to what extent muscle cross-sectional area of the lower leg (mCSA) and tibial structural strength are influenced by common and trait-specific genetic and environmental factors. pQCT scans were obtained from both members of 102 monozygotic (MZ) and 113 dizygotic (DZ) 63- to 76-yr-old female twin pairs to estimate the mCSA of the lower leg, structural bending strength of the tibial shaft (BSIbend), and compressive strength of the distal tibia (BSIcomp). Quantitative genetic models were used to decompose the phenotypic variances into common and trait-specific additive genetic (A), shared environmental (C), and individual environmental (E) effects. The …
Twins. Similarities, differences and individuality
2015
This study aims to investigate the self-differentiating perceptions and the separation-individuation’s process in emerging adulthood twins. A group of 40 Italian pairs of twins (21 couples dizygotic-DZ and 19 monozygotic-MZ) aged 20-30 years, were evaluated using the test of graphic projection Family Life Space (DSSVF) and thought a specific questionnaire ad hoc constructed for this research. The research hypothesis focus on Zazzo’s test of parallel testimony and provide to give empirical evidence about the capacity of MZ Twins to use more internal resources of the couple than DZ Twins, causing the split slowdown on identification. The data show that there are no difference between not bise…
Genetics of maximal walking speed and skeletal muscle characteristics in older women.
2008
AbstractThe aim of this study was to examine whether maximal walking speed, maximal isometric muscle strength, leg extensor power and lower leg muscle cross-sectional area (CSA) shared a genetic effect in common. In addition, we wanted to identify the chromosomal areas linked to maximal walking speed and these muscle characteristics and also investigate whether maximal walking speed and these three skeletal muscle characteristics are regulated by the same chromosomal areas. We studied 217 monozygotic (MZ) and dizygotic (DZ) female twin pairs aged 66 to 75 years in the Finnish Twin Study on Aging study. The DZ pairs (94) were genotyped for 397 microsatellite markers in 22 autosomes and X-chr…