Heritability of a linear combination of traits

Summary The heritability, h _I ² , of a linear combination of phenotypes, I, when defined as the ratio of the variance of the genetic index, _g ² *, to the variance of the index, _I ² , is shown to be different from the square of the correlation, r _HI ² , between the index and an arbitrary linear combination of genetic effects, H. The gain in H fror selection on I is shown to be proportional to h _I ² . b_Hg for any index.Approved for publication as Journal Article No. 183-76 of the Ohio Agricultural Research and Development Center, Wooster, Ohio 44691.     

QTL analysis of morphological traits in a tomato recombinant inbred line population.

Quantitative trait loci (QTLs) influencing morphological traits were identified by restriction fragment length polymorphism (RFLP) analysis in a population of recombinant inbred lines (RILs) derived from a cross of the cultivated tomato Lycopersicon esculentum with a related wild species, Lycopersicon cheesmanii. One hundred and thirty-two RFLP loci spaced throughout the tomato genome were used as DNA probes on genomic DNA from 97 RIL families. Morphological traits, including plant height, plant fresh mass, number of branches, number of nodes, first flower-bearing node, and leaf length, were evaluated in two controlled environment trials in 1992 and 1993. QTLs were detected via regression analyses at multiple marker loci for each morphological trait. A total of 41 markers were significantly associated with the traits examined. Large additive effects were measured at many of these loci. QTLs for multiple traits were detected on chromosomes 3 (TG74) and 4 (CT188), suggesting the possible association of these chromosome segments with genes controlling growth and development in tomato. These chromosomal regions were also associated with multiple morphological traits in a L. esculentum x Lycopersicon pennellii cross. A total of 13% of the QTLs identified for traits common to both studies occupied similar map positions.     

Heritability of quantitative orbital traits

We conducted a study of 63 couples and their 242 normal children from northeastern Brazil (no facial malformations or deformities) to evaluate the heritability of 4 quantitative traits of the orbital region adjusted by covariance for sex, age, (age)2, sex x age, and sex x (age)2. The heritability is estimated as 0.514 for the mean horizontal diameter of the palpebral fissures, 0.454 for the interpupillary distance, 0.390 for the internal intercanthal distance, and 0.337 for the external intercanthal distance. The heritability of the first principal component of the orbital region is estimated as 0.418.     

Heritability of metabolic syndrome traits in a large population-based sample

Heritability estimates of metabolic syndrome traits vary widely across studies. Some studies have suggested that the contribution of genes may vary with age or sex. We estimated the heritability of 11 metabolic syndrome-related traits and height as a function of age and sex in a large population-based sample of twin families (N = 2,792–27,021, for different traits). A moderate-to-high heritability was found for all traits [from H² = 0.47 (insulin) to H² = 0.78 (BMI)]. The broad-sense heritability (H²) showed little variation between age groups in women; it differed somewhat more in men (e.g., for glucose, H² = 0.61 in young females, H² = 0.56 in older females, H² = 0.64 in young males, and H²= 0.27 in older males). While nonadditive genetic effects explained little variation in the younger subjects, nonadditive genetic effects became more important at a greater age. Our findings show that in an unselected sample (age range, ∼18–98 years), the genetic contribution to individual differences in metabolic syndrome traits is moderate to large in both sexes and across age. Although the prevalence of the metabolic syndrome has greatly increased in the past decades due to lifestyle changes, our study indicates that most of the variation in metabolic syndrome traits between individuals is due to genetic differences.     

Assortative mating for anthropometric traits in parents of Punjabi twins

The marital correlations between 97 pairs of parents of Punjabi twins reveal positive phenotypic assortative mating for body traits while almost random mating with respect to cranio-facial traits. There is no evidence of any significant negative assortative mating for any of the 50 traits. The results have been compared with those from other world populations. The data contradict the earlier reported hypothesis that assortative mating is associated with lowered fertility.     

Genetic basis of variation in morphological and life-history traits of a wild population of pink salmon

Understanding the genetic basis of phenotypic variation is essential for predicting the direction and rate of phenotypic evolution. We estimated heritabilities and genetic correlations of morphological (fork length, pectoral and pelvic fin ray counts, and gill arch raker counts) and life-history (egg number and individual egg weight) traits of pink salmon (Oncorhynchus gorbuscha) from Likes Creek, Alaska, in order to characterize the genetic basis of phenotypic variation in this species. Families were created from wild-caught adults, raised to the fry stage in the lab, released into the wild, and caught as returning adults and assigned to families using microsatellite loci and a growth hormone locus. Morphological traits were all moderately to highly heritable, but egg number and egg weight were not heritable, suggesting that past selection has eliminated additive genetic variation in egg number and egg weight or that there is high environmental variance in these traits. Genetic correlations were similar for nonadjacent morphological traits and adjacent traits. Genetic correlations predicted phenotypic correlations fairly accurately, but some pairs of traits with low genetic correlations had high phenotypic correlations, and vice versa, emphasizing the need to use caution when using phenotypic correlations as indices of genetic correlations. This is one of only a handful of studies to estimate heritabilities and genetic correlations for a wild population.     

Heritability estimates for carcass traits of cattle: a review

We present estimates of heritability for carcass traits of cattle published in the scientific literature. Seventy-two papers published from 1962 to 2004, which reported estimates of heritability for carcass traits, were reviewed. The unweighted means of estimates of heritability for 14 carcass traits by slaughter end point (age, weight, and fat depth) were calculated. Among the three end points, carcass weight, backfat thickness, longissimus muscle area, and marbling score were the carcass traits with the most estimates of heritability (56 相似文献   

Pedigree analysis and inbreeding effects over morphological traits in Campolina horse population

Genetic improvement, without control of inbreeding, can go to loss of genetic variability, reducing the potential for genetic gains in the domestic populations. The aim of this study was to analyze the population structure and the inbreeding depression in Campolina horses. Phenotype information from 43 465 individuals was analyzed, data provided by the Campolina Breeders Association. A pedigree file containing 107 951 horses was used to connected the phenotyped individuals. The inbreeding coefficient was performed by use of the diagonal of the relationship matrix and the genealogical parameters were computed using proper softwares. The effective population size was estimated based on the rate of inbreeding and census information, and the stratification of the population was verified by the average relationship coefficient between animals born in different regions of Brazil. The effects of inbreeding on morphological traits were made by the use of inbreeding coefficient as a covariate in the model of random regression. The inbreeding coefficient increased from 1990 on, impacting effective population size and, consequently, shrinking genetic variability. The paternal inbreeding was greater than maternal, which may be attributed to the preference for inbred animals in reproduction. The average genetic relationship coefficient of animals born in different states was lower than individuals born within the same state. The increase in the inbreeding coefficient was negatively associated with all studied traits, showing the importance to avoid genetic losses in the long term. Although results do not indicate a severe narrowing of the population until the present date, the average relationship coefficient shows signs of increase, which could cause a drastic reduction in genetic variability if inbred mating is not successfully controlled in the Campolina horse population.     

Emergence of deciduous teeth in Punjabi children, north India.

Data on deciduous tooth emergence of 312 children aged 4 to 31 months of Punjabi parentage are presented. Probit analysis was used to derive the median age of tooth emergence. Female children are found to be advanced with respect to tooth emergence than their male counterparts. While comparing the present data with those from other populations it is found that, in general, the mean number of emerged teeth in Punjabi children is more at most ages, with lower median age of eruption for most teeth. Magnitude of interage variability in the eruption times is noticed to be maximum in the 16-17 and 20-21 months age groups. The findings of the study suggest that number of teeth can be used as a parameter for the estimation of age.     

‘Heritability’ of dispersal propensity in a patchy population

Although dispersal is often considered to be a plastic, condition-dependent trait with low heritability, growing evidence supports medium to high levels of dispersal heritability. Obtaining unbiased estimates of dispersal heritability in natural populations nevertheless remains crucial to understand the evolution of dispersal strategies and their population consequences. Here we show that dispersal propensity (i.e. the probability of dispersal between habitat patches) displays a significant heritability in the collared flycatcher Ficedula albicollis, as estimated by within-family resemblance when accounting for environmental factors. Offspring of dispersing mothers or fathers had a higher propensity to disperse to a new habitat patch themselves. The effect of parental dispersal status was additional to that of local habitat quality, as measured by local breeding population size and success, confirming previous results about condition-dependent dispersal in this population. The estimated levels of heritability varied between 0.30±0.07 and 0.47±0.10, depending on parent–offspring comparisons made and correcting for a significant assortative mating with respect to dispersal status. Siblings also displayed a significant resemblance in dispersal propensity. These results suggest that variation in between-patch natal dispersal in the collared flycatcher is partly genetically determined, and we discuss ways to quantify this genetic basis and its implications.     

Heritability of cardiovascular and personality traits in 6,148 Sardinians

In family studies, phenotypic similarities between relatives yield information on the overall contribution of genes to trait variation. Large samples are important for these family studies, especially when comparing heritability between subgroups such as young and old, or males and females. We recruited a cohort of 6,148 participants, aged 14–102 y, from four clustered towns in Sardinia. The cohort includes 34,469 relative pairs. To extract genetic information, we implemented software for variance components heritability analysis, designed to handle large pedigrees, analyze multiple traits simultaneously, and model heterogeneity. Here, we report heritability analyses for 98 quantitative traits, focusing on facets of personality and cardiovascular function. We also summarize results of bivariate analyses for all pairs of traits and of heterogeneity analyses for each trait. We found a significant genetic component for every trait. On average, genetic effects explained 40% of the variance for 38 blood tests, 51% for five anthropometric measures, 25% for 20 measures of cardiovascular function, and 19% for 35 personality traits. Four traits showed significant evidence for an X-linked component. Bivariate analyses suggested overlapping genetic determinants for many traits, including multiple personality facets and several traits related to the metabolic syndrome; but we found no evidence for shared genetic determinants that might underlie the reported association of some personality traits and cardiovascular risk factors. Models allowing for heterogeneity suggested that, in this cohort, the genetic variance was typically larger in females and in younger individuals, but interesting exceptions were observed. For example, narrow heritability of blood pressure was approximately 26% in individuals more than 42 y old, but only approximately 8% in younger individuals. Despite the heterogeneity in effect sizes, the same loci appear to contribute to variance in young and old, and in males and females. In summary, we find significant evidence for heritability of many medically important traits, including cardiovascular function and personality. Evidence for heterogeneity by age and sex suggests that models allowing for these differences will be important in mapping quantitative traits.     

Within- and between-zygosity variance in oral traits among US and Punjabi twins

Cross-cultural comparison of twin variances reveals widespread heterogeneity among zygosities for dental occlusal traits, implying various biases in calculation of genetic variance or heritability estimates. These estimates are fairly robust for dental size traits, however. Differences in pattern between Punjabi (Northwest Indian) and American twins highlight the environmental differences that affect heritability determinations.     

Heritability and genetic correlations of personality traits in a wild population of yellow‐bellied marmots (Marmota flaviventris)

Describing and quantifying animal personality is now an integral part of behavioural studies because individually distinctive behaviours have ecological and evolutionary consequences. Yet, to fully understand how personality traits may respond to selection, one must understand the underlying heritability and genetic correlations between traits. Previous studies have reported a moderate degree of heritability of personality traits, but few of these studies have either been conducted in the wild or estimated the genetic correlations between personality traits. Estimating the additive genetic variance and covariance in the wild is crucial to understand the evolutionary potential of behavioural traits. Enhanced environmental variation could reduce heritability and genetic correlations, thus leading to different evolutionary predictions. We estimated the additive genetic variance and covariance of docility in the trap, sociability (mirror image stimulation), and exploration and activity in two different contexts (open‐field and mirror image simulation experiments) in a wild population of yellow‐bellied marmots (Marmota flaviventris). We estimated both heritability of behaviours and of personality traits and found nonzero additive genetic variance in these traits. We also found nonzero maternal, permanent environment and year effects. Finally, we found four phenotypic correlations between traits, and one positive genetic correlation between activity in the open‐field test and sociability. We also found permanent environment correlations between activity in both tests and docility and exploration in the MIS test. This is one of a handful of studies to adopt a quantitative genetic approach to explain variation in personality traits in the wild and, thus, provides important insights into the potential variance available for selection.     

Obesity prevalence and nutritional habits among Indian women: a comparison between Punjabi women living in India and Punjabi migrants in Vienna, Austria

The current study aimed to determine the prevalence of obesity and overweight among Indian women living in Punjab, India and in Vienna, Austria. A series of 115 women ageing between 17 and 80 years (x = 38.7 yrs; +/- 14.5) was enrolled in the present study. 65 women lived in the district of Jalandhar in Punjab, 50 Punjabi women lived in as migrants in Vienna Austria. Data collection comprised an anthropometric analysis including stature height, body weight and the body mass index (BMI). For classification of the weight status the Indian BMI cutoffs defined by the WHO for Asian Indians were used. Data concerning dietary patterns and lifestyle parameters were collected by structured interviews using a standardized questionnaire. Among both subgroups overweight and obesity were highly prevalent. Underweight (18.5%) was significantly more prevalent in Punjab than in Vienna (6.0 %), while overweight and obesity were more frequently found among Punjabi women in Vienna (26.0%; 54.0%) than among Punjabi women in India (9.2%; 24.6 %). Analysing lifestyle and dietary patterns it turned out that energy dense meals were preferred and fat and sugar were used frequently among both subsamples. A statistically significant relationship between dietary habits and weight status could not be proved.