Investigating the genetic control of complex traits (original) (raw)
Related papers
Principles and biological concepts of heredity before Mendel
Biology Direct, 2021
The knowledge of the history of a subject stimulates understanding. As we study how other people have made scientific breakthroughs, we develop the breadth of imagination that would inspire us to make new discoveries of our own. This perspective certainly applies to the teaching of genetics as hallmarked by the pea experiments of Mendel. Common questions students have in reading Mendel’s paper for the first time is how it compares to other botanical, agricultural, and biological texts from the early and mid-nineteenth centuries; and, more precisely, how Mendel’s approach to, and terminology for debating, topics of heredity compare to those of his contemporaries? Unfortunately, textbooks are often unavailing in answering such questions. It is very common to find an introduction about heredity in genetic textbooks covering Mendel without mentions of preceding breeding experiments carried out in his alma mater. This does not help students to understand how Mendel came to ask the questi...
Principles of Inheritance: Mendel's Laws and Genetic Models
It is difficult to overstate the impact of Mendel's research on the history of genetics; indeed, his research in genetics has been credited as one of the great experimental advances in biology (Fisher, 1965). Prior to the publication of his results on experimental hybridization in plants, the concept of inheritance of physical 'units' (later called genes) was accepted, and scientists had reported on many hybridization experiments in both animals and plants. Yet no one had set forth principles of inheritance which could be used as a universal theory to explain how traits in offspring can be predicted from traits in the parents. Mendel provided an explicit rule for how the genotypes of the offspring can be predicted from the genotypes of their parents, and he also established models for how genotypes were related to traits. This is nothing short of astonishing in view of the fact that genes and genotypes were not observed; rather their existence was inferred from the phenotypes that were observed. Needless to say, the underlying biology of cell division and the process of formation of sperm and egg cells was not then known; otherwise the derivation of Mendel's laws would be more straightforward.
Gregor Mendel and the History of Heredity
2018
Gregor Mendel’s paper "Experiments on Plant Hybrids" (1866) has become a paradigmatic case in the historiography of the life sciences because production and reception of a “discovery” sharply fell apart, thus raising fundamental questions about the relationship between scientific achievement and “its” time. In this chapter, I am providing an overview of answers that have been given to these questions by various historians. In a first section, I cover commentators who have claimed that Mendel was “ahead” of his time, and that contemporaries failed to recognize his achievement. I then move on to scholars and scientists who argued against this position, claiming that Mendel was not anticipating twentieth-century genetics, but was in fact representative of an older research tradition. In a last step, I turn to the more recent cultural history of heredity according to which Mendel was embedded in a local culture that combined a variety of advanced and traditional strands of nineteenth-century life-sciences. Overall, I am arguing that one should not overestimate the coherence and dominance of presumed “paradigms”, “epistemes” or “styles” in biology.
Darwin and Mendel: evolution and genetics
Many studies have shown that students' understanding of evolution is low and some sort of historical approach would be necessary in order to allow students to understand the theory of evolution. It is common to present Mendelian genetics to high school students prior to Biological Evolution, having in mind historical and epistemological assumptions regarding connections between the works of Gregor Mendel and Charles Darwin. It is often said that Darwin 'lacked' a theory of heredity and, therefore, he had not been able to produce the synthetic theory of evolution himself. Thus, schools could provide a prior basis for heredity, so that students could begin to study evolution with a proper background in genetics. We intend to review some research on the history of biology, attempting to show that, even if Darwin had had notice of Mendel's works – which we think he did – he would not have changed his views on heredity. We examine this belief and its possible origins, offer some considerations about Darwin's views on heredity, including his knowledge of the 3:1 ratio, the consequences for the work on Nature of Science (NOS), and finally give five reasons to consider alternative possibilities for curriculum development.
MENDEL IN GENETICS TEACHING: SOME CONTRIBUTIONS FROM HISTORY OF SCIENCE AND ARTICLES FOR TEACHERS
School science descriptions about Mendel and his story are problematic because several statements that are controversial among historians of science are repeated over and over again as if they were established facts. Another problem is the neglect of other scientists working on inheritance in the second half of the 19th century, including Darwin, Spencer, Galton, Nägeli, Brooks, Weismann and de Vries, who paved the way for the reinterpretation of Mendel’s work in 1900. These problems are often found in textbooks and are likely to be present in school science throughout the world. Here, we discuss the contributions that history of science and papers published in journals that target teachers may bring to improve how school science deals with Mendel and his contributions. Evidently the idea is not that school teachers could solve problems still under discussion in the historical literature. The point is, rather, that it is important to avoid treating Mendel’s contributions as uncontroversial, mentioning, for instance, that there are ongoing debates on whether he proposed the laws named after him, appealing to invisible factors underlying phenotypic traits that are seen as the heritable potentials for those traits, and would in due time be known as genes. History of science can contribute to put the mythic Mendel into question in the science classroom, bringing school science closer to the controversies around the interpretation of his work.
Mendel is credited for discovering Laws of Heredity, but his work has come under criticism on three grounds: for possible falsification of data to fit his expectations, for getting undue credit for the laws of heredity without having ideas of segregation and independent assortment, and for being interested in the development of hybrids rather than in the laws of heredity. I present a brief review of these criticisms and conclude that Mendel deserved to be called the father of genetics even if he may not, and most likely did not, have clear ideas of segregation and particulate determiners as we know them now. I argue that neither Mendel understood the evolutionary significance of his findings for the problem of genetic variation, nor would Darwin have understood their significance had he read Mendel's paper. I argue that the limits to imagination, in both cases, came from their mental framework being shaped by existing paradigms-blending inheritance in the case of Darwin, hybrid development in the case of Mendel. Like Einstein, Darwin's natural selection was deterministic; like Niels Bohr, Mendel's Laws were probabilistic-based on random segregation of trait-determining "factors". Unlike Einstein who understood quantum mechanics, Darwin would have been at a loss with Mendel's paper with no guide to turn to. Geniuses in their imaginations are like heat-seeking missiles locked-in with their targets of deep interests and they generally see things in one dimension only. Imagination has limits; unaided imagination is like a bird without wingsit goes nowhere.
The role played by natural selection on Mendelian traits in humans
Annals of the New York Academy of Sciences, 2010
Detecting whether and how natural selection has targeted regions of the human genome represents a complementary strategy for identifying functionally important loci and variants involved in disease resistance and adaptation to the environment. In contrast with most complex diseases or traits, the genetic architecture of most Mendelian traits is relatively well established. Most mutations associated with Mendelian disease-related traits are highly penetrant and kept at low population frequencies because of the effects of purifying selection. However, this is not always the case. Here, we review several examples of Mendelian mutations-associated with various disease conditions or other traits of anthropological interest-that have increased in frequency in the human population as a result of past positive selection. These examples clearly illustrate the value of a population genetics approach to unravel the biological mechanisms that have been central to our past and present survival against the selective pressures imposed by diseases and other environmental factors.