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Results for “quantitative genetics”

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At least 253 records · Page 14Linked to original sources
PubMed1987

Zinc-induced peripheral anosmia and behavioral responses to novelty in mice: a quantitative-genetic analysis.

Adult male mice were made anosmic by intranasal flushing with a 5% zinc sulfate solution. Twelve behavioral variables were measured in treated as well as saline-irrigated control animals placed in a novel environment. The genetic underpinnings and the genotype-treatment interactions with regard to these behaviors were analyzed in a classical Mendelian cross between the inbred strains C57BL/6 and DBA/2 and in a full 4 X 4 diallel cross, replicated five times, between these strains and strains C3H/St an CPB-K. Based on the hypothesis of an evolutionary history of directional selection for a well-balanced information-processing system, one might expect directional dominance for decrease in exploration after anosmization. Although decreases were found for several behavioral phenotypes, only few and relatively unimportant genotype-treatment interactions were present. This absence of any kind of genetic variation for behavioral change after anosmization points to an extremely strong directional selection which has eliminated all less favorable alleles. The findings support the hypothesis of directional selection for an efficient olfactory information-processing system.

Animals↗
PubMed2002

Quantitative genetic modeling of regional brain volumes and cognitive performance in older male twins.

As part of an ongoing longitudinal twin study, data from both MRI brain scanning and from neuropsychological testing were obtained from 139 male-male twin pairs (72 monozygotic [MZ] and 67 dizygotic [DZ]), 69-80 years old at the time of examination. For descriptive purposes, we examined the MZ and DZ intraclass correlations (ICC) of four lobar brain volumes (frontal, temporal, parietal, and occipital), two cerebrospinal fluid (CSF) volumes (lateral ventricle and temporal horn of the lateral ventricles), and two measures of cognitive functioning (verbal memory and executive function). We found that for lobar brain and CSF space volumes, the MZ ICC were significantly greater than zero (r=0.37-0.77) and greater than the corresponding DZ correlations (r=0.02-0.49). Similarly, within-pair correlations for the two neuropsychological factors were statistically significant and significantly larger in MZ twin pairs than in DZ pairs, suggesting the presence of genetic variance. Bivariate genetic analysis revealed that while close to 60% of individual differences in neuropsychological performance were due to genetic influences, less than 50% of genetic effects were in common with those influencing brain volumes. These data may shed light on the genetic liability for brain diseases that affect the elderly.

Aged↗
PubMed2003

A quantitative genetic analysis of schizotypal personality traits.

BACKGROUND: Previous twin studies investigating the heritability of schizotypy have often had limited power and have failed to measure the disorganization/social anxiety component. METHOD: Seven hundred and thirty-three female twin pairs, drawn from the Institute of Psychiatry Volunteer Twin Register, completed the Oxford-Liverpool Inventory of Feelings and Experiences and the Peters et al. Delusions Inventory. Structural equation modelling was carried out on scores for MZ and DZ twin pairs. RESULTS: The best fitting models for all scales comprised additive genetic and unique environmental effects. Heritability was estimated at approximately 50% for most scales, although it was lower at 37% for the PDI scale. Multivariate structural equation model fitting revealed a best-fitting model in which additive genetic and unique environmental influences act through a single common pathway for Cognitive Disorganization, Unusual Experiences and the PDI, and through a separate common pathway for Cognitive Disorganization and Introvertive Anhedonia. CONCLUSIONS: The various components of schizotypy are moderately heritable. Multivariate model fitting indicates that at least two latent factor structures are required to account for the covariation between the various components of schizotypy. The positive and negative components of schizotypy are relatively genetically independent, although each in turn may be related to Cognitive Disorganization.

Adolescent↗
PubMed1999

Quantitative genetic variation for oviposition preference with respect to phenylthiocarbamide in Drosophila melanogaster.

Seven isogenic strains of Drosophila melanogaster were assayed for oviposition preference on food with phenylthiocarbamide (PTC) versus plain food. There was significant variation among strains for the percentage of eggs oviposited on each medium, ranging from 70 +/- 4% (SE) preference for plain food to no significant preference. Reciprocal hybrid, backcross, and F2 generations derived from two extreme parent strains revealed significant additive and nonadditive genetic variation but no evidence of maternal, paternal, or sex-chromosome effects.

Animals↗
PubMed2001

A quantitative genetic study of cephalometric variables in twins.

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.

Journal Article↗
PubMed2005

Quantitative genetic analysis of latent growth curve models of cognitive abilities in adulthood.

Though many cognitive abilities exhibit marked decline over the adult years, individual differences in rates of change have been observed. In the current study, biometrical latent growth models were used to examine sources of variability for ability level (intercept) and change (linear and quadratic effects) for verbal, fluid, memory, and perceptual speed abilities in the Swedish Adoption/Twin Study of Aging. Genetic influences were more important for ability level at age 65 and quadratic change than for linear slope at age 65. Expected variance components indicated decreasing genetic and increasing nonshared environmental variation over age. Exceptions included one verbal and two memory measures that showed increasing genetic and nonshared environmental variance. The present findings provide support for theories of the increasing influence of the environment with age on cognitive abilities.

Adoption↗
PubMed1987

Quantitative genetics and fitness: lessons from Drosophila.

This paper examines patterns of heritability and genetic covariance between traits in the genus Drosophila. Traits are divided into the categories, morphology, behaviour, physiology and life history. Early theoretical analyses suggested that life history traits should have heritabilities that are lower than those in other categories. Variable pleiotrophy, environmental variation, mutation and niche variation may, however, maintain high heritabilities. In Drosophila the heritabilities of life history traits are lower than morphological or physiological traits but may exceed 20 per cent. The pattern of variation in the heritability of behavioural traits is similar to that of life history traits. Genetic covariance between morphological traits and between morphological and life history traits are all positive but those between life history traits have variable sign. Negative covariance between traits supports the variable pleiotropy hypothesis but other factors such as environmental heterogeneity, or mutation cannot be excluded.

Animals↗
PubMed1989

Quantitative genetic analysis of courtship and reproduction in female Drosophila melanogaster.

Three hundred mother-daughter pairs were analyzed for seven attributes related to courtship and reproduction. Only the lag time from first courtship to copulation was significantly heritable; genetic correlations involving this attribute were not significant. The genetic correlation between fertility and lag time to first courtship was negative and significant. However, this genetic correlation is expected to have little impact on the retention of additive genetic variance or on response to selection because it involves two attributes with low heritabilities. The pattern of phenotypic covariation among traits is largely explained by environmental causes and is consistent with that found in a previous analysis of father-son pairs (Gromko, 1987).

Alleles↗
PubMed1990

Quantitative genetic background effects on the Antennapaedia phenotype in Drosophila melanogaster.

Genetic background variation influencing expression of the Antennapaedia homeotic phenotype was examined by crossing the Antp73b allele of the Antennapaedia locus reciprocally into seven isogenically derived wild type strains of Drosophila melanogaster and their genetically heterogeneous parent strain, Dover. The parent Antp73b strain's Antennapaedia phenotype shows a small patch of untransformed antennal tissue remaining on the homeotic femur. The size of this patch was used as an assay for background variation influencing expression of the Antp73b homeotic mutation. Patch size varied approximately six-fold across the different genetic backgrounds. Effects of maternal parent, sex, and sex-linkage were also observed.

Animals↗
PubMed2006

Quantitative genetic analysis of blood pressure reactivity to orthostatic tilt using principal components analysis.

Blood pressure (BP) reactivity to orthostatic tilt may be predictive of cardiovascular disease. However, the genetic and environmental influences on BP reactivity to tilt have not been well examined. Identifying different influences on BP at rest and BP during tilt is complicated by the intercorrelation among multiple measurements. In this study, we use principal components analysis (PCA) to reduce multivariate BP data into components that are orthogonal. The objective of this study is to characterize and examine the genetic architecture of BP at rest and during head-up tilt (HUT). Specifically, we estimate the heritability of individual BP measures and three principal components (PC) derived from multiple BP measurements during HUT. Additionally, we estimate covariate effects on these traits. The study sample consisted of 444 individuals, distributed across four large families. HUT consisted of 70 degrees head-up table tilting while strapped to a tilt table. BP reactivity (deltaBP) was defined as BP during HUT minus BP while supine. Three PC extracted from the PCA were interpreted as 'general BP' (PC1), 'pulse pressure' (PC2) and 'BP reactivity' (PC3). Variance components methods were used to estimate the heritabilities of resting BP, HUT BP, deltaBP, as well as the three BP PC. Significant (P<0.05) heritabilities were found for all BP measurements, except for systolic deltaBP at 1 and 3 min, and diastolic deltaBP at 2 min. Significant genetic effects were also found for the three PC. Each of these orthogonal components is significantly influenced by somewhat different sets of covariates.

Adolescent↗