Darwin’s contributions to genetics

Darwin’s contributions to evolutionary biology are well known, but his contributions to genetics are much less known. His main contribution was the collection of a tremendous amount of genetic data, and an attempt to provide a theoretical framework for its interpretation. Darwin clearly described almost all genetic phenomena of fundamental importance, such as prepotency (Mendelian inheritance), bud variation (mutation), heterosis, reversion (atavism), graft hybridization (Michurinian inheritance), sex-limited inheritance, the direct action of the male element on the female (xenia and telegony), the effect of use and disuse, the inheritance of acquired characters (Lamarckian inheritance), and many other observations pertaining to variation, heredity and development. To explain all these observations, Darwin formulated a developmental theory of heredity — Pangenesis — which not only greatly influenced many subsequent theories, but also is supported by recent evidence.     

The kin of the gene: the medicalization of family and kinship in American Society

In the past several decades there has been an explosion of research in genetics and on genetic inheritance. This new genetics is part of contemporary biomedicine and forecasts great advances in alleviating disease and prolonging human life. It also encompasses notions about biological family and kinship relations. I propose that with the advent of the new genetics, family and kinship are being medicalized. I explore the ways in which explanations of the inheritance of genetic disease influence people's understandings of family and kin and both reflect and conflict with broader current sociocultural processes. The discussion includes a brief overview of the anthropological study of kinship, the meaning of family and kinship in contemporary society, the concept of medicalization and its implications for people's lives as seen through narratives and concludes with an analysis the significance of the medicalization of family and kinship in present-day society.     

Some history of heredity-vs-environment, genetic inferiority at Harvard(?), and The (incredible) Bell Curve

This article discusses some historical and intellectual roots of American behaviorism in psychology and its anti-heredity, environmentalist bias, as well as the early ‘justification’ for pure line theory in genetics and some interrelations between the two fields. Next, I discuss the heritability concept, its promotion, its critique and the importance of distinguishing it from, rather than confusing or conflating it with, the heredity concept. Then, briefly I consider some of the history and problems associated with the intelligence concept, as well as the capital importance of biological controls in studies of human heredity. And finally, I document the incredibility of The Bell Curve and the appalling inadequacy of its reception. This revised version was published online in August 2006 with corrections to the Cover Date.     

The frame of non-canonical theory of heredity: from genes to epigenes

Particular theory of heredity that exceeds the limits of mendelian genetics is suggested. The model based on five sufficiently obvious assumptions (accepted as axioms) As consequence of these axioms the strict statements concerningfunctional heredity memory were formulated in mathematical terms. Molecular-genetic realization of the memory cells appears as new class of heredity units--epigenes. In the epigenes part f hereditary information is contained, encoded and transmitted beyond the primary structure of DNA molecules of genome. Epigenes capable to conserve sequences of genes functional states in the course of ontogenesis and provide transmission of information contained in this states throw consequent generations. It was shown that epigenes differ from genes at least by encoding method of heredity information. There are three functional-equivalent classes of really existing epigenes mechanisms: dynamic, modificational and transpositional; and there is one hypothetical class--invertional. It was shown that a lot of experimental data concerning epigenetic mechanism of heredity is in accord with theoretical conclusions concerning epigenes existence. Moreover, we constructed an artificial epigenes by genetic engineering methods. The existence of epigenes means that obtaining complete genome sequence, its physical and genetic maps, as well as distinguishing the rules of genes function encoding by its primary structure do not provide complete decoding of hereditary information. The role of epigenes in ontogenesis and phylogenesis was examined. It was shown that even elementary epigenetic systems could determine key ontogenesis events. Epigenetic system could serve as the basis of non-darwinian evolutionary strategies by means of "memorization of rather unsuccessfully steps of evolution" and conservation of alternative variants of ontogenesis. Teleonomic hypothesis on functional heredity memory was formulated. This theory provides explanation of phenomena of acquired features inheritance and molecular mechanisms of stress-induced evolution.     

Compositional Inheritance: Comparison of Self-assembly and Catalysis

Genetic inheritance in modern cells is due to template-directed replication of nucleic acids. However, the difficulty of prebiotic synthesis of long information-carrying polymers like RNA raises the question of whether some other form of heredity is possible without polymers. As an alternative, the lipid world theory has been proposed, which considers non-covalent assemblies of lipids, such as micelles and vesicles. Assemblies store information in the form of a non-random molecular composition, and this information is passed on when the assemblies divide, i.e. the assemblies show compositional inheritance. Here, we vary several important assumptions of previous lipid world models and show that compositional inheritance is relevant more generally than the context in which it was originally proposed. Our models assume that interaction occurs between nearest neighbour molecules only, and account for spatial segregation of molecules of different types within the assembly. We also draw a distinction between a self-assembly model, in which the composition is determined by mutually favourable interaction energies between the molecules, and a catalytic model, in which the composition is determined by mutually favourable catalysis. We show that compositional inheritance occurs in both models, although the self-assembly case seems more relevant if the molecules are simple lipids. In the case where the assemblies are composed of just two types of molecules, there is a strong analogy with the classic two-allele Moran model from population genetics. This highlights the parallel between compositional inheritance and genetic inheritance.     

Darwin and Mendel: who was the pioneer of genetics?

Although Mendel is now widely recognized as the founder of genetics, historical studies have shown that he did not in fact propose the modern concept of paired characters linked to genes, nor did he formulate the two "Mendelian laws" in the form now given. Furthermore, Mendel was accused of falsifying his data, and Mendelism has been met with scepticism because of its failure to provide scientific explanation for evolution, to furnish a basis for the process of genetic assimilation and to explain the inheritance of acquired characters, graft hybridization and many other facts. Darwin was the first to clearly describe almost all genetical phenomena of fundamental importance, and was the first to present a developmental theory of heredity--Pangenesis, which not only greatly influenced many subsequent theories of inheritance, particularly those of de Vries, Galton, Brooks and Weismann, but also tied all aspects of variation, heredity and development together, provided a mechanism for most of the observable facts, and is supported by increasing evidence. It has also been indicated that Darwin's influence on Mendel, primarily from The Origin, is evident. The word "gene" was derived from "pangen", itself a derivative of "Pangenesis" which Darwin had coined. It seems that Darwin should have been regarded as the pioneer, if not of transmissional genetics, of developmental genetics and molecular genetics.     

Gregor Mendel's classic paper and the nature of science in genetics courses

The discoveries of Gregor Mendel, as described by Mendel in his 1866 paper Versuche uber Pflanzen-Hybriden (Experiments on plant hybrids), can be used in undergraduate genetics and biology courses to engage students about specific nature of science characteristics and their relationship to four of his major contributions to genetics. The use of primary source literature as an instructional tool to enhance genetics students' understanding of the nature of science helps students more clearly understand how scientists work and how the science of genetics has evolved as a discipline. We offer a historical background of how the nature of science developed as a concept and show how Mendel's investigations of heredity can enrich biology and genetics courses by exemplifying the nature of science.     

Quantifying Characters: Polygenist Anthropologists and the Hardening of Heredity

Scholars studying the history of heredity suggest that during the 19th-century biologists and anthropologists viewed characteristics as a collection of blended qualities passed on from the parents. Many argued that those characteristics could be very much affected by environmental circumstances, which scholars call the inheritance of acquired characteristics or “soft” heredity. According to these accounts, Gregor Mendel reconceived heredity – seeing distinct hereditary units that remain unchanged by the environment. This resulted in particular traits that breed true in succeeding generations, or “hard” heredity. The author argues that polygenist anthropology (an argument that humanity consisted of many species) and anthropometry in general should be seen as a hardening of heredity. Using a debate between Philadelphia anthropologist and physician, Samuel G. Morton, and Charleston naturalist and reverend, John Bachman, as a springboard, the author contends that polygenist anthropologists hardened heredity by conceiving of durable traits that might reappear even after a race has been eliminated. Polygenists saw anthropometry (the measurement of humans) as one method of quantifying hereditary qualities. These statistical ranges were ostensibly characteristics that bred true and that defined racial groups. Further, Morton’s interest in hybridity and racial mixing demonstrates that the polygenists focused as much on the transmission and recognition of “amalgamations” of characters as they did on racial categories themselves. The author suggests that seeing race science as the study of heritable, statistical characteristics rather than broad categories helps explain why “race” is such a persistent cultural phenomenon.     

Notions of heredity in the correspondence of Edwin Grant Conklin

This article examines five letters from the correspondence of American zoologist Edwin Grant Conklin that highlight his theories of genetic and social inheritance, in order to suggest that Conklin's eugenic beliefs--like those of many American authorities during this time--were complex and sometimes contradictory. The letters reveal the international prestige of American science after the two world wars and illuminate key moments in the emergence of the concepts of heredity and inheritance, within both the science of genetics and the social movement of eugenics.     

From genetics of intraspecific differences to genetics of intraspecific similarity

Based on the Mendelian approach to heredity, modern genetics describes inheritance of characters belonging to the category of intraspecific difference. The other large category of characters, intraspecific similarity, stays out of investigation. In this review, the genome part responsible for intraspecific similarity is considered as invariant and regulatory. An approach to studying the invariant part of the Drosophila melanogaster genome is formulated and the results of examining this genome part are presented. The expression of mutations at genes in the invariant genome part is different from that of Mendelian genes. We conclude that these genes are present in the genome in multiple copies and they are functionally haploid in the diploid genome. Severe abnormalities of development appearing in the progeny of mutant parents suggest that the mutant genes are genes regulating ontogeny. A hypothesis on an elementary ontogenetic event is advanced and the general scheme of ontogeny is presented. A concept on two types of gene allelism (cis- and trans-allelism) is formulated. This approach opens a possibility for studying genetic material responsible for the formation of intraspecific similarity characters at different taxonomic levels on the basis of crossing individuals of the same species.     

Kin selection under blending inheritance

Why did Darwin fail to develop his insights on kin selection into a proper theory of social adaptation? One suggestion has been that his inadequate understanding of heredity kept the problem out of focus. Here, I determine whether it is possible to develop a quantitative theory of kin selection upon the assumption of blending inheritance. I find that, whilst Hamilton's rule of kin selection can be readily derived under the assumption of blending inheritance, this mechanism complicates the computation of relatedness coefficients, and can even cause them to fluctuate over generations. Nevertheless, I show that the ultimate criterion for selection to favour any social trait - i.e. a time-average of Hamilton's rule - remains the same as under particulate inheritance. By eliminating the gene from the theory of kin selection, I clarify the role that it plays in the theory of social adaptation.     

Ideas about heredity, genetics, and 'medical genetics' in Britain, 1900-1982

The aim of this paper is to understand how evolving ideas about heredity and genetics influenced new medical interests and practices and, eventually, the formation of 'medical genetics' as a medical specialism in Britain. I begin the paper by highlighting the social and institutional changes through which these ideas passed. I argue that, with time, there was a decisive convergence in thought that combined ideas about the familial aspects of heredity and the health needs of populations with an omnibus 'genetic' approach to health and illness that focused on the structures and activities of chromosomes and genes in individuals. I show how this convergence in thought was spurred on, first, by innovations in genetic science and technology in the years after 1960, and, second, by negotiated protocols and standards of medical practice worked out by bodies such as the relevant royal colleges, the linked associations and societies for medical professionals, affected training and research authorities, and the state. The notion of 'medical genetics' in Britain consequently gained a semblance of unanimity over its basic reference points and arrived at a meaning directly tributary to current acceptance of the term in the context of a medical specialism.     

重提达尔文的遗传学说——泛生论

长期以来, 达尔文的遗传学说--泛生论(Pangenesis)被认为是错误的。一是泛生论解释的一些现象(如嫁接杂交和获得性遗传)的真实性一直被怀疑, 二是高尔顿的兔子输血实验获得了负面结果, 三是达尔文假定的由细胞释放出来的并可以在体内循环的遗传分子“微芽”(Gemmules)缺乏实验证据。但近年科学文献中积累了许多支持获得性遗传和嫁接杂交的实验证据。循环核酸的发现则说明生物体内确实存在可以在细胞间移动的遗传物质。文章简要介绍达尔文的泛生论及其被湮灭的原因, 并结合自己的工作, 介绍支持泛生论的新证据及我们对泛生论的再认识。重新认识达尔文的泛生论, 对遗传学、医学和进化生物学等领域都有重要意义。     

Asthma genetics and intermediate phenotypes: a review from twin studies.

It has been long recognised that asthma and related phenotypes have an important hereditary nature, in which inheritance does not follow the classical Mendelian patterns and the exact mode of inheritance is not known. Linkage, association studies and genome-wide screening suggest that many genes are involved in the pathogenesis of asthma. Twin studies have contributed significantly to our understanding on the genetics of asthma, especially the large-scale twin studies in different parts of the world which have showed comparable results. With the shortcomings of the twin method borne in mind, more twin studies are needed to investigate the heredity component of the intermediate phenotypes of asthma, that is, bronchial hyperresponsiveness, total immunoglobulin E, skin test reactivity, specific IgE against different aeroallergens, and the variability of lung function. Twin studies are very suitable to unravel the intricate network of genes and environment which plays a role in asthma. Monozygotic twins and the co-twin control design are suitable for this purpose, while longitudinal twin studies are needed to solve the problem of the age related expression of genes which probably are involved in the pathogenesis of asthma. In the near future twin studies will play an important role in the detection of new, as yet undiscovered genes, but may be even more important in answering the most challenging of all questions: how do the environment interact with the genetics of asthma? Exchange of information and collaboration between the different research groups involved in the genetics of asthma will contribute to a better understanding of this condition.     

Investigating protein conformation-based inheritance and disease in yeast

Our work supports the hypothesis that a protein can serve as an element of genetic inheritance. This protein-only mechanism of inheritance is propagated in much the same way as hypothesized for the transmission of the protein-only infectious agent in the spongiform encephalopathies; hence these protein factors have been called yeast prions. Our work has focused on [PSI(+)], a dominant cytoplasmically inherited factor that alters translational fidelity.This change in translation is produced by a self-perpetuating change in the conformation of the translation-termination factor, Sup35. Most recently, we have determined that new elements of genetic inheritance can be created by deliberate genetic engineering, opening prospects for new methods of manipulating heredity. We have also uncovered evidence that other previously unknown elements of protein-based inheritance are encoded in the yeast genome. Finally, we have begun to use yeast as a model system for studying human protein folding diseases, such as Huntington's disease. Proteins responsible for some of these diseases have properties uncannily similar to those that produce protein-based mechanisms of inheritance.     

Self-replicating protein conformations and information transfer: The adaptive β-sheet model

The deposition of proteins with a highly ordered β-sheet conformation is characteristic of several amyloid diseases. However, recent data indicate that amyloid formation is not always pathological, but may also be physiological. Based on the new insights in understanding the structural arrangements and the self-propagating properties of the β-conformational proteins in combination with the progress in elucidating the mechanisms of prion genetics and chaperone-controlled protein folding, a model of an adaptive β-sheet information system was developed. The idea is advanced that exogenous information can be specifically stored in the protease-resistant β-sheet rich protein aggregates in a prion-like mode creating a cytoplasmic molecular memory. The conformationally-bound information can then be transmitted to next cell generations by way of the self-propagating potential of the amyloidogenic structure. Controlled by a network of input-sensitive molecular chaperones, the β-conformation based information system could constitute a form of soft inheritance characterized by adaptability and plasticity. It is suggested that the β-system represents an evolutionary conserved primordial inheritance mechanism based on protein conformation.     

以人类血型为遗传学案例教学的思考与实践

血型是人类日常生活中非常常见的一种遗传表型, 拥有丰富的遗传学内涵。随着科技的发展, 其内涵不断得到新的揭示, 新的研究结果不断补充, 持续吸引着人们对血型遗传机制的探索。血型遗传案例除了与孟德尔遗传和连锁遗传、基因突变和染色体畸变四大内容关联外, 还涉及到其他多方面的遗传学知识点。在教学中, 依据遗传学的知识脉络, 贯穿以ABO血型作为经典案例, 结合拓展的白细胞血型, 孟买、Rh、MN等血型的遗传规律及其应用, 并且开展相关的实验教学, 理论联系实际, 增强了学生的兴趣, 提高了教学效果。在遗传学实验教学中, 有80%的学生选择ABO血型鉴定这个自选实验, 并表示出对这个实验的浓厚兴趣。在讲授相关知识点时, 用恰当的血型案例为引导, 设计相关的讨论主题, 开展PPT展示性讨论和辩论式讨论, 所有的学生都积极主动参与进来, 与现实生活相结合, 引导学生思考问题, 使学生的思维在辨析中得到操练, 提高分析问题和解决问题的能力, 深刻理解遗传学基本理论知识。     

From Genetics of Intraspecific Differences to Genetics of Intraspecific Similarity

Based on the Mendelian approach to heredity, modern genetics describes inheritance of characters belonging to the category of intraspecific difference. the other large category of characters,intraspecific similarity, stays out of investigation. In this review, the genome part responsible for intraspecific similarity is considered as invariant and regulatory. An approach to studying the invariant part of the Drosophila melanogaster genome is formulated and the results of examining this genome part are presented. The expression of mutations at genes in the invariant genome part is different from that of Mendelian genes. We conclude that these genes are present in the genome in multiple copies and they are functionally haploid in the diploid genome. Severe abnormalities of development appearing in the progeny of mutant parents suggest that the mutant genes are genes regulating ontogeny. A hypothesis on an elementary ontogenetic event is advanced and the general scheme of ontogeny is presented. A concept on two types of gene allelism (cis- and trans-allelism) is formulated. This approach opens a possibility for studying genetic material responsible for the formation of intraspecific similarity characters at different taxonomic levels on the basis of crossing individuals of the same species.