Heritability in the genome-wide association era

Heritability, the fraction of phenotypic variation explained by genetic variation, has been estimated for many phenotypes in a range of populations, organisms, and time points. The recent development of efficient genotyping and sequencing technology has led researchers to attempt to identify the genetic variants responsible for the genetic component of phenotype directly via GWAS. The gap between the phenotypic variance explained by GWAS results and those estimated from classical heritability methods has been termed the "missing heritability problem". In this work, we examine modern methods for estimating heritability, which use the genotype and sequence data directly. We discuss them in the context of classical heritability methods, the missing heritability problem, and describe their implications for understanding the genetic architecture of complex phenotypes.     

蚜虫基因组及功能基因组研究进展

蚜虫作为刺吸式昆虫和植物病毒的传播者,已经成为严重威胁农业生产发展的重要害虫之一。近几年随着分子生物学的发展,尤其是基因组测序技术的进步,蚜虫基因组学和功能基因组学取得了重大突破,使我们对蚜虫特殊的生物学特征有了深层次的认识。本文就蚜虫与内共生菌关系、表型可塑性、发育和生殖、系统进化、解毒酶基因家族以及唾液腺方面在基因组和功能基因组水平上的研究进展进行了综述。     

Common student misconceptions in exercise physiology and biochemistry

The present study represents a preliminary investigation designed to identify common misconceptions in students' understanding of physiological and biochemical topics within the academic domain of sport and exercise sciences. A specifically designed misconception inventory (consisting of 10 multiple-choice questions) was administered to a cohort of level 1, 2, and 3 undergraduate students enrolled in physiology and biochemistry-related modules of the BSc Sport Science degree at the authors' institute. Of the 10 misconceptions proposed by the authors, 9 misconceptions were confirmed. Of these nine misconceptions, only one misconception appeared to have been alleviated by the current teaching strategy employed during the progression from level 1 to 3 study. The remaining eight misconceptions prevailed throughout the course of the degree program, suggesting that students enter and leave university with the same misconceptions in certain areas of exercise physiology and biochemistry. The possible origins of these misconceptions are discussed, as are potential teaching strategies to prevent and/or remediate them for future years.     

Two misconceptions of phylogeny and classification

A recent contribution embodies the assumptions that organisms may be excluded from relationship with others on the basis of autopomorphy, and that its position in a classification is an inherent characteristic of an organism. Both of these assumptions are fallacious.     

Integrating sequence, evolution and functional genomics in regulatory genomics

With genome analysis expanding from the study of genes to the study of gene regulation, 'regulatory genomics' utilizes sequence information, evolution and functional genomics measurements to unravel how regulatory information is encoded in the genome.     

Biobanks for genomics and genomics for biobanks

Biobanks include biological samples and attached databases. Human biobanks occur in research, technological development and medical activities. Population genomics is highly dependent on the availability of large biobanks. Ethical issues must be considered: protecting the rights of those people whose samples or data are in biobanks (information, autonomy, confidentiality, protection of private life), assuring the non-commercial use of human body elements and the optimal use of samples and data. They balance other issues, such as protecting the rights of researchers and companies, allowing long-term use of biobanks while detailed information on future uses is not available. At the level of populations, the traditional form of informed consent is challenged. Other dimensions relate to the rights of a group as such, in addition to individual rights. Conditions of return of results and/or benefit to a population need to be defined. With 'large-scale biobanking' a marked trend in genomics, new societal dimensions appear, regarding communication, debate, regulation, societal control and valorization of such large biobanks. Exploring how genomics can help health sector biobanks to become more rationally constituted and exploited is an interesting perspective. For example, evaluating how genomic approaches can help in optimizing haematopoietic stem cell donor registries using new markers and high-throughput techniques to increase immunogenetic variability in such registries is a challenge currently being addressed. Ethical issues in such contexts are important, as not only individual decisions or projects are concerned, but also national policies in the international arena and organization of democratic debate about science, medicine and society.     

Dispelling the myths and misconceptions about transumbilical breast augmentation

Since its invention in 1991, the transumbilical breast augmentation (TUBA) technique has gained popularity, and it has been proven safe and effective. In addition, the technique has several advantages over other methods of breast augmentation. Nevertheless, the method has often been the subject of a great variety of criticisms. Careful examination of those criticisms reveals that most are, in fact, untrue; they are misconceptions at best and falsehoods at worst. In this article, the author examines the 20 most common misconceptions about this procedure, clarifies or corrects them as appropriate, and suggests possible reasons for their having arisen in the first place. In addition, the actual drawbacks of the technique are reviewed. The author also outlines what he considers to be the criteria necessary for a surgeon to criticize any technique being used successfully by others: the surgeon must have proper plastic surgical training and certification, have completed training in the specific technique, and have a personal experience with performing a minimum number of cases.     

Lifetime Reproductive Success and Heritability in Nature

The observation that traits closely related to fitness ("fitness traits") have lower heritabilities than traits more distantly associated with fitness has traditionally been framed in terms of Fisher's fundamental theorem of natural selection-fitness traits are expected to have low levels of additive genetic variance due to rapid fixation of alleles conferring highest fitness. Subsequent treatments have challenged this view by pointing out that high environmental and nonadditive genetic contributions to phenotypic variation may also explain the low heritability of fitness traits. Analysis of a large data set from the collared flycatcher Ficedula albicollis confirmed a previous finding that traits closely associated with fitness tend to have lower heritability. However, analysis of coefficients of additive genetic variation (CVA) revealed that traits closely associated with fitness had higher levels of additive genetic variation (VA) than traits more distantly associated with fitness. Hence, the negative relationship between a trait's association with fitness and its heritability was not due to lower levels of VA in fitness traits but was due to their higher residual variance. However, whether the high residual variance was mainly due to higher levels of environmental variance or due to higher levels of nonadditive genetic variance remains a challenge to be addressed by further studies. Our results are consistent with earlier suggestions that fitness-related traits may have more complex genetic architecture than traits more distantly associated with fitness.     

Heritability: uses and abuses

This paper begins with a brief summary of the history of the development of ideas in the field of quantitative genetics. Next there is discussion of the controversy surrounding the contention that IQ tests validly estimate some highly heritable general intelligence factor. The validity of the reasoning supporting this contention is questioned. The theory of correlation between relatives has been of vast importance in plant and animal breeding because it is possible to design and carry out experiments to estimate variance components in expressions for covariances between relatives. However, data on humans is observational and individuals are not randomly assigned to environments, so that estimation of heritability from such data is not on the same firm foundation as it is in plant and animal breeding contexts. This revised version was published online in August 2006 with corrections to the Cover Date.     

Functional genomics in the mouse

The mouse is the premier genetic model organism for the study of human disease and development. With the recent advances in sequencing of the human and mouse genomes, there is strong interest now in large-scale approaches to decipher the function of mouse genes using various mutagenesis technologies. This review discusses what tools are currently available for manipulating and mutagenizing the mouse genome, such as ethylnitrosourea and gene trap mutagenesis, engineered inversions and deletions using the cre-lox system, and proviral insertional mutagenesis in somatic cells, and how these are being used to uncover gene function. Electronic Publication     

Equality in Educational Policy and the Heritability of Educational Attainment

Secular variation in the heritability of educational attainment are proposed to be due to the implementation of more egalitarian educational policies leading to increased equality in educational opportunities in the second part of the 20^th century. The action of effect is hypothesized to be a decrease of shared environmental (e.g., family socioeconomic status or parents’ education) influences on educational attainment, giving more room for genetic differences between individuals to impact on the variation of the trait. However, this hypothesis has not yet found consistent evidence. Support for this effect relies mainly on comparisons between countries adopting different educational systems or between different time periods within a country reflecting changes in general policy. Using a population-based sample of 1271 pairs of adult twins, we analyzed the effect of the introduction of a specific educational policy in Spain in 1970. The shared-environmental variance decreased, leading to an increase in heritability in the post-reform cohort (44 vs. 67%) for males. Unstandardized estimates of genetic variance were of a similar magnitude (.56 vs. .57) between cohorts, while shared environmental variance decreased from .56 to .04. Heritability remained in the same range for women (40 vs. 34%). Our results support the role of educational policy in affecting the relative weight of genetic and environmental factors on educational attainment, such that increasing equality in educational opportunities increases heritability estimates by reducing variation of non-genetic familial origin.