Graham Bell
- Published in print:
- 2007
- Published Online:
- May 2008
- ISBN:
- 9780198569725
- eISBN:
- 9780191717741
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198569725.003.0004
- Subject:
- Biology, Evolutionary Biology / Genetics
The evolution of asexual organisms in laboratory microcosms is constrained by the lack of genetic exchange and by isolation from the rest of the world. When these constraints are relaxed, the rate of ...
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The evolution of asexual organisms in laboratory microcosms is constrained by the lack of genetic exchange and by isolation from the rest of the world. When these constraints are relaxed, the rate of adaptation and how it is acquired may change. The first section in this chapter is called Horizontal transmission and details gene transfer agents; gene cassettes; and conjugative plasmids. The second section is entitled Sex and it explains all about dominance; sorting in asexual diploid populations; sorting in sexual diplonts; heterozygotes; recombination; the limits to adaptation; purifying selection in sexual populations: mutation clearance; synthetic lethal mutations; mean fitness under purifying selection; directional selection in sexual populations: mutation assembly; directional selection in sexual populations: mutation liberation; the effect of recombination in phage; the effect of sex in microbes; the effect of recombination in Drosophila; and finally sex and the response to selection. The third section is about dispersal and informs on population structure; subdivided asexual populations; subdivided sexual diploid populations; the shifting balance.Less
The evolution of asexual organisms in laboratory microcosms is constrained by the lack of genetic exchange and by isolation from the rest of the world. When these constraints are relaxed, the rate of adaptation and how it is acquired may change. The first section in this chapter is called Horizontal transmission and details gene transfer agents; gene cassettes; and conjugative plasmids. The second section is entitled Sex and it explains all about dominance; sorting in asexual diploid populations; sorting in sexual diplonts; heterozygotes; recombination; the limits to adaptation; purifying selection in sexual populations: mutation clearance; synthetic lethal mutations; mean fitness under purifying selection; directional selection in sexual populations: mutation assembly; directional selection in sexual populations: mutation liberation; the effect of recombination in phage; the effect of sex in microbes; the effect of recombination in Drosophila; and finally sex and the response to selection. The third section is about dispersal and informs on population structure; subdivided asexual populations; subdivided sexual diploid populations; the shifting balance.
Samir Okasha
- Published in print:
- 2006
- Published Online:
- January 2007
- ISBN:
- 9780199267972
- eISBN:
- 9780191708275
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199267972.003.0006
- Subject:
- Philosophy, Philosophy of Science
This chapter examines the notorious issue of group selection in behavioural ecology, one of the mainstays of the traditional levels of selection debate. The history of the group selection controversy ...
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This chapter examines the notorious issue of group selection in behavioural ecology, one of the mainstays of the traditional levels of selection debate. The history of the group selection controversy is briefly traced. The relationship between group selection, kin selection, and evolutionary game theory is discussed. An important debate between Sober and Wilson and Maynard Smith concerning the correct way to conceptualize group selection is explored. Lastly, some arguments of L. Nunney concerning the distinction between weak and strong altruism, and how individual and group selection should be defined, are examined.Less
This chapter examines the notorious issue of group selection in behavioural ecology, one of the mainstays of the traditional levels of selection debate. The history of the group selection controversy is briefly traced. The relationship between group selection, kin selection, and evolutionary game theory is discussed. An important debate between Sober and Wilson and Maynard Smith concerning the correct way to conceptualize group selection is explored. Lastly, some arguments of L. Nunney concerning the distinction between weak and strong altruism, and how individual and group selection should be defined, are examined.
Paul F. Lurquin and Linda Stone
- Published in print:
- 2007
- Published Online:
- September 2007
- ISBN:
- 9780195315387
- eISBN:
- 9780199785674
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195315387.003.0002
- Subject:
- Religion, Religion and Society
This chapter describes the Darwin-Wallace theory of evolution by natural selection. In particular, it explains the notion of fitness, which underlies the concepts of descent with modification and the ...
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This chapter describes the Darwin-Wallace theory of evolution by natural selection. In particular, it explains the notion of fitness, which underlies the concepts of descent with modification and the appearance of species categorized into clades. It shows that descent with modification is a much better evolutionary theory than the “Great chain of being” model, which implies that evolution is driven toward the production of more perfect and complex life-forms. Finally, it explains how the science of genetics strongly supports evolution through the notions of mutation, gene frequencies in populations, and drift.Less
This chapter describes the Darwin-Wallace theory of evolution by natural selection. In particular, it explains the notion of fitness, which underlies the concepts of descent with modification and the appearance of species categorized into clades. It shows that descent with modification is a much better evolutionary theory than the “Great chain of being” model, which implies that evolution is driven toward the production of more perfect and complex life-forms. Finally, it explains how the science of genetics strongly supports evolution through the notions of mutation, gene frequencies in populations, and drift.
Graham Bell
- Published in print:
- 2007
- Published Online:
- May 2008
- ISBN:
- 9780198569725
- eISBN:
- 9780191717741
- Item type:
- book
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198569725.001.0001
- Subject:
- Biology, Evolutionary Biology / Genetics
Adaptation is caused by selection continually winnowing the genetic variation created by mutation. In the last ten years, our knowledge of how selection operates on populations in the field and in ...
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Adaptation is caused by selection continually winnowing the genetic variation created by mutation. In the last ten years, our knowledge of how selection operates on populations in the field and in the laboratory has increased enormously, and this book aims to provide an up-to-date account of selection as the principal agent of evolution. In the classical Fisherian model, weak selection acting on many genes of small effect over long periods of time is responsible for driving slow and gradual change. It is now clear that adaptation in laboratory populations often involves strong selection acting on a few genes of large effect, while in the wild selection is often strong and highly variable in space and time. These results are changing our perception of how evolutionary change takes place. This book summarizes current understanding of the causes and consequences of selection, with an emphasis on quantitative and experimental studies. It includes material on experimental evolution, natural selection in the wild, artificial selection, selfish genetic elements, and selection in social contexts, sexual selection, and speciation.Less
Adaptation is caused by selection continually winnowing the genetic variation created by mutation. In the last ten years, our knowledge of how selection operates on populations in the field and in the laboratory has increased enormously, and this book aims to provide an up-to-date account of selection as the principal agent of evolution. In the classical Fisherian model, weak selection acting on many genes of small effect over long periods of time is responsible for driving slow and gradual change. It is now clear that adaptation in laboratory populations often involves strong selection acting on a few genes of large effect, while in the wild selection is often strong and highly variable in space and time. These results are changing our perception of how evolutionary change takes place. This book summarizes current understanding of the causes and consequences of selection, with an emphasis on quantitative and experimental studies. It includes material on experimental evolution, natural selection in the wild, artificial selection, selfish genetic elements, and selection in social contexts, sexual selection, and speciation.
Ádám Miklósi
- Published in print:
- 2007
- Published Online:
- January 2008
- ISBN:
- 9780199295852
- eISBN:
- 9780191711688
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199295852.003.0005
- Subject:
- Biology, Animal Biology
This chapter deals with one of the most long-debated question about how dogs became domesticated. Traditional understanding of this process was based on the finding of archaeologists that are, ...
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This chapter deals with one of the most long-debated question about how dogs became domesticated. Traditional understanding of this process was based on the finding of archaeologists that are, however, restricted to only a few geographic locations and time periods. The possibility of scientific inquiry about domestication has changed with the introduction of novel phylogenetic approaches based on molecular biological methods, which, however, are also not without problems. The chapter provides an introduction to constraints presented by both the archaeological and the phylogenetic investigations, and reviews the problems of tracing genetic evolution. Finally, a possible multi-step framework for dog domestication is presented.Less
This chapter deals with one of the most long-debated question about how dogs became domesticated. Traditional understanding of this process was based on the finding of archaeologists that are, however, restricted to only a few geographic locations and time periods. The possibility of scientific inquiry about domestication has changed with the introduction of novel phylogenetic approaches based on molecular biological methods, which, however, are also not without problems. The chapter provides an introduction to constraints presented by both the archaeological and the phylogenetic investigations, and reviews the problems of tracing genetic evolution. Finally, a possible multi-step framework for dog domestication is presented.
Graham Bell
- Published in print:
- 2007
- Published Online:
- May 2008
- ISBN:
- 9780198569725
- eISBN:
- 9780191717741
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198569725.003.0001
- Subject:
- Biology, Evolutionary Biology / Genetics
The action of selection is based on a few simple principles that are general to all self-replicating systems, and which constitute a distinct branch of science. This introductory chapter presents a ...
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The action of selection is based on a few simple principles that are general to all self-replicating systems, and which constitute a distinct branch of science. This introductory chapter presents a brief overview of some of these principles in a wide range of systems. It is divided into various sections on the following discussion topics: RNA viruses are the simplest self-replicators; exponential growth can be maintained by serial transfer; replication is always imprecise; imprecise replication leads to differential growth; selection acts directly on rates of replication; selection may act indirectly on other characters; the indirect response to selection is often antagonistic; evolution typically involves a sequence of alterations; the evolution of increased complexity is a contingent process; very improbable structures rapidly arise through the cumulation of alterations; competitors are an important part of the environment; evolution through selection is a property of self-replicators; self-replicating algorithms evolve in computers; and finally evolution through selection is governed by a set of general principles.Less
The action of selection is based on a few simple principles that are general to all self-replicating systems, and which constitute a distinct branch of science. This introductory chapter presents a brief overview of some of these principles in a wide range of systems. It is divided into various sections on the following discussion topics: RNA viruses are the simplest self-replicators; exponential growth can be maintained by serial transfer; replication is always imprecise; imprecise replication leads to differential growth; selection acts directly on rates of replication; selection may act indirectly on other characters; the indirect response to selection is often antagonistic; evolution typically involves a sequence of alterations; the evolution of increased complexity is a contingent process; very improbable structures rapidly arise through the cumulation of alterations; competitors are an important part of the environment; evolution through selection is a property of self-replicators; self-replicating algorithms evolve in computers; and finally evolution through selection is governed by a set of general principles.
Graham Bell
- Published in print:
- 2007
- Published Online:
- May 2008
- ISBN:
- 9780198569725
- eISBN:
- 9780191717741
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198569725.003.0002
- Subject:
- Biology, Evolutionary Biology / Genetics
This chapter gives some quantitative information about the rates of genetic and environmental deterioration. The first section in this chapter is about history, chance, and necessity, and includes ...
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This chapter gives some quantitative information about the rates of genetic and environmental deterioration. The first section in this chapter is about history, chance, and necessity, and includes subsections on Lamarckian evolution; the selection of undirected variation; descent; and delection. The second section is about drift and includes subsections concerning the rate of genetic deterioration; two scaled mutation rates; the rate of deleterious mutation; decay of isolate lines in the absence of selection; mutation rate in other replicators; mutation rate in stressful environments; the genomic mutation rate; the effect of mutations; beneficial mutations; the effect of gene deletion on growth; the rate of accumulation of genetic variance in fitness; the replication limit; the size spectrum; the distribution of species abundance; and finally genetic variation and species abundance. The final section is on the rate of environmental deterioration. Subsections in this section concern aggregation; the ecological population concept; dispersal; and the genetic population concept. Five theories of the environment are offered and environmental variation in space; environmental variation over time; and the biotic environment are also detailed.Less
This chapter gives some quantitative information about the rates of genetic and environmental deterioration. The first section in this chapter is about history, chance, and necessity, and includes subsections on Lamarckian evolution; the selection of undirected variation; descent; and delection. The second section is about drift and includes subsections concerning the rate of genetic deterioration; two scaled mutation rates; the rate of deleterious mutation; decay of isolate lines in the absence of selection; mutation rate in other replicators; mutation rate in stressful environments; the genomic mutation rate; the effect of mutations; beneficial mutations; the effect of gene deletion on growth; the rate of accumulation of genetic variance in fitness; the replication limit; the size spectrum; the distribution of species abundance; and finally genetic variation and species abundance. The final section is on the rate of environmental deterioration. Subsections in this section concern aggregation; the ecological population concept; dispersal; and the genetic population concept. Five theories of the environment are offered and environmental variation in space; environmental variation over time; and the biotic environment are also detailed.
Pamela C. Ronald and Raoul W. Adamchak
- Published in print:
- 2008
- Published Online:
- May 2008
- ISBN:
- 9780195301755
- eISBN:
- 9780199867196
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195301755.003.0007
- Subject:
- Biology, Plant Sciences and Forestry
This chapter discusses the potential risk and benefits of GE. For most humans, all the essentials of life — food, family, and work have associated risks. Does GE technology have potential for saving ...
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This chapter discusses the potential risk and benefits of GE. For most humans, all the essentials of life — food, family, and work have associated risks. Does GE technology have potential for saving children's lives through reduced exposure to pesticides or increased nutrients in their diet?Less
This chapter discusses the potential risk and benefits of GE. For most humans, all the essentials of life — food, family, and work have associated risks. Does GE technology have potential for saving children's lives through reduced exposure to pesticides or increased nutrients in their diet?
Diana B. Petitti
- Published in print:
- 2009
- Published Online:
- May 2010
- ISBN:
- 9780195398441
- eISBN:
- 9780199776023
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195398441.003.0032
- Subject:
- Public Health and Epidemiology, Public Health, Epidemiology
Hemochromatosis encompasses issues of importance to basic scientists, clinical researchers, clinicians, epidemiologists, public health professionals, and policy makers. Understanding its history, the ...
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Hemochromatosis encompasses issues of importance to basic scientists, clinical researchers, clinicians, epidemiologists, public health professionals, and policy makers. Understanding its history, the evolution of our knowledge about it, and the current state of knowledge, provides rich insights into the genetics of disease and the complexity of the genetic determinants of disease and health in humans. This chapter discusses the discovery of hemochromatosis, the classification of hemochromatosis, population screening for mutations that cause hereditary hemochromatosis, and the selective screening of high-risk groups.Less
Hemochromatosis encompasses issues of importance to basic scientists, clinical researchers, clinicians, epidemiologists, public health professionals, and policy makers. Understanding its history, the evolution of our knowledge about it, and the current state of knowledge, provides rich insights into the genetics of disease and the complexity of the genetic determinants of disease and health in humans. This chapter discusses the discovery of hemochromatosis, the classification of hemochromatosis, population screening for mutations that cause hereditary hemochromatosis, and the selective screening of high-risk groups.
Edward C. Holmes and Andrew Rambaut
- Published in print:
- 2005
- Published Online:
- September 2007
- ISBN:
- 9780198568193
- eISBN:
- 9780191718175
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198568193.003.0003
- Subject:
- Biology, Disease Ecology / Epidemiology
RNA viruses experience rates of mutation that are some six orders of magnitude higher than those seen in eukaryotes, which undoubtedly gives them great adaptability. Paradoxically, these mutation ...
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RNA viruses experience rates of mutation that are some six orders of magnitude higher than those seen in eukaryotes, which undoubtedly gives them great adaptability. Paradoxically, these mutation rates also constrain virus evolution by putting a cap on genome size through the imposition of an ‘error-threshold’. This chapter starts with an overview of the major constraints and trade-offs in RNA virus evolution in general. In particular coronaviruses, including that which causes SARS, represent an interesting variant on this theme because they have the longest genomes of any RNA virus — at ~32 kb compared to the median of ~9 kb seen in other RNA viruses. It therefore seems that coronaviruses have been able to escape the constraints on genome size imposed by the error-threshold. The chapter discusses how SARS coronavirus has achieved this unique expansion in genome size, and what it means for the long-term evolution of this virus.Less
RNA viruses experience rates of mutation that are some six orders of magnitude higher than those seen in eukaryotes, which undoubtedly gives them great adaptability. Paradoxically, these mutation rates also constrain virus evolution by putting a cap on genome size through the imposition of an ‘error-threshold’. This chapter starts with an overview of the major constraints and trade-offs in RNA virus evolution in general. In particular coronaviruses, including that which causes SARS, represent an interesting variant on this theme because they have the longest genomes of any RNA virus — at ~32 kb compared to the median of ~9 kb seen in other RNA viruses. It therefore seems that coronaviruses have been able to escape the constraints on genome size imposed by the error-threshold. The chapter discusses how SARS coronavirus has achieved this unique expansion in genome size, and what it means for the long-term evolution of this virus.
Joshua S. Weitz
- Published in print:
- 2016
- Published Online:
- October 2017
- ISBN:
- 9780691161549
- eISBN:
- 9781400873968
- Item type:
- chapter
- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691161549.003.0004
- Subject:
- Biology, Disease Ecology / Epidemiology
This chapter discusses the evolutionary dynamics of viruses. Preexisting variation in host phenotypes include variants with different levels of susceptibility to viruses, including complete ...
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This chapter discusses the evolutionary dynamics of viruses. Preexisting variation in host phenotypes include variants with different levels of susceptibility to viruses, including complete resistance. Formative studies of the basis of the mutation rate relied upon virus–host interactions and the possibility of the evolution of resistance to infection. Viruses represent a strong selective pressure and can induce evolution among hosts. Host evolution, as induced by viruses, includes novel forms of ecological dynamics, including cryptic dynamics. Infection of hosts represents a strong selective pressure for viruses. Viruses that differ in their life history traits vary in their fitness and can invade and replace existing viral strains. The latent period represents a model trait for the further study of the evolution of intermediate phenotypes. Evolution among other traits is also possible, including who infects whom.Less
This chapter discusses the evolutionary dynamics of viruses. Preexisting variation in host phenotypes include variants with different levels of susceptibility to viruses, including complete resistance. Formative studies of the basis of the mutation rate relied upon virus–host interactions and the possibility of the evolution of resistance to infection. Viruses represent a strong selective pressure and can induce evolution among hosts. Host evolution, as induced by viruses, includes novel forms of ecological dynamics, including cryptic dynamics. Infection of hosts represents a strong selective pressure for viruses. Viruses that differ in their life history traits vary in their fitness and can invade and replace existing viral strains. The latent period represents a model trait for the further study of the evolution of intermediate phenotypes. Evolution among other traits is also possible, including who infects whom.
Joshua S. Weitz
- Published in print:
- 2016
- Published Online:
- October 2017
- ISBN:
- 9780691161549
- eISBN:
- 9781400873968
- Item type:
- chapter
- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691161549.003.0005
- Subject:
- Biology, Disease Ecology / Epidemiology
This chapter discusses coevolutionary dynamics of viruses and microbes. Virus mutation and host mutations occur rapidly, so much so that new virus and host mutants are expected to arise on timescales ...
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This chapter discusses coevolutionary dynamics of viruses and microbes. Virus mutation and host mutations occur rapidly, so much so that new virus and host mutants are expected to arise on timescales similar to those for changes in total population. Host evolution to resistance can lead to virus extinction, but such extinction is not inevitable either in the lab or in the field. A single dominant host and virus type can, via a combination of mutation and selection, diversify into multiple virus and host types that coexist in one community. The interaction of multiple virus and host genotypes has fundamental effects on ecological dynamics. When multiple virus and host genotypes are present, their interactions can lead to novel ecological dynamics, such as apparently reversed predator–prey cycles. Moreover, the interactions of a single virus–host pair can lead to distinct modes of evolutionary dynamics, for example, fluctuating dynamics, arms races, and diversification.Less
This chapter discusses coevolutionary dynamics of viruses and microbes. Virus mutation and host mutations occur rapidly, so much so that new virus and host mutants are expected to arise on timescales similar to those for changes in total population. Host evolution to resistance can lead to virus extinction, but such extinction is not inevitable either in the lab or in the field. A single dominant host and virus type can, via a combination of mutation and selection, diversify into multiple virus and host types that coexist in one community. The interaction of multiple virus and host genotypes has fundamental effects on ecological dynamics. When multiple virus and host genotypes are present, their interactions can lead to novel ecological dynamics, such as apparently reversed predator–prey cycles. Moreover, the interactions of a single virus–host pair can lead to distinct modes of evolutionary dynamics, for example, fluctuating dynamics, arms races, and diversification.
Denis J. Murphy
- Published in print:
- 2007
- Published Online:
- September 2007
- ISBN:
- 9780199207145
- eISBN:
- 9780191708893
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199207145.003.0015
- Subject:
- Biology, Plant Sciences and Forestry
The expansion of the British and Dutch mercantile empires from the 17th century was accompanied by a renewal of the old Babylonian concept of Imperial Botany, now made all the more effective by a new ...
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The expansion of the British and Dutch mercantile empires from the 17th century was accompanied by a renewal of the old Babylonian concept of Imperial Botany, now made all the more effective by a new marriage of private commerce with state power and scientific knowledge. By the 18th century, and largely thanks to agrarian entrepreneurs such as Townshend, Coke, and Tull, Britain was undergoing an agricultural revolution that would underpin the later industrial revolution and consequent population growth. Botany became all the rage in court circles across Europe, from Vienna to Madrid. Botanical gardens established throughout the Anglo-Dutch empires simultaneously served economic, scientific, and aesthetic purposes. Crops such as sugar, tea, coffee, and cocoa served both as stimuli for expansion and lucrative products for the maturing empires. Greater understanding of the mechanisms of plant reproduction enabled breeders to experiment with new hybrids and mutations in order to enhance crop variation.Less
The expansion of the British and Dutch mercantile empires from the 17th century was accompanied by a renewal of the old Babylonian concept of Imperial Botany, now made all the more effective by a new marriage of private commerce with state power and scientific knowledge. By the 18th century, and largely thanks to agrarian entrepreneurs such as Townshend, Coke, and Tull, Britain was undergoing an agricultural revolution that would underpin the later industrial revolution and consequent population growth. Botany became all the rage in court circles across Europe, from Vienna to Madrid. Botanical gardens established throughout the Anglo-Dutch empires simultaneously served economic, scientific, and aesthetic purposes. Crops such as sugar, tea, coffee, and cocoa served both as stimuli for expansion and lucrative products for the maturing empires. Greater understanding of the mechanisms of plant reproduction enabled breeders to experiment with new hybrids and mutations in order to enhance crop variation.
John C. Avise
- Published in print:
- 2010
- Published Online:
- May 2010
- ISBN:
- 9780195393439
- eISBN:
- 9780199775415
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195393439.003.0002
- Subject:
- Biology, Evolutionary Biology / Genetics
This chapter addresses the history and current state of knowledge about human inborn errors of metabolism. Mutations in protein‐coding genes slaughter or maim countless individuals (especially ...
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This chapter addresses the history and current state of knowledge about human inborn errors of metabolism. Mutations in protein‐coding genes slaughter or maim countless individuals (especially embryos and fetuses) and promote legions of genetic disabilities in our species. Included in this chapter are empirical examples from the many thousands of known instances in which standard “good‐housekeeping” genes occasionally go bad, via deleterious mutations, and thereby contribute to the morbid anatomy of the human genome. Collectively, humanity bears a heavy genetic load from these genetic disorders, a fact that poses profound interpretive challenges for both science and religion.Less
This chapter addresses the history and current state of knowledge about human inborn errors of metabolism. Mutations in protein‐coding genes slaughter or maim countless individuals (especially embryos and fetuses) and promote legions of genetic disabilities in our species. Included in this chapter are empirical examples from the many thousands of known instances in which standard “good‐housekeeping” genes occasionally go bad, via deleterious mutations, and thereby contribute to the morbid anatomy of the human genome. Collectively, humanity bears a heavy genetic load from these genetic disorders, a fact that poses profound interpretive challenges for both science and religion.
Norman A. Johnson
- Published in print:
- 2007
- Published Online:
- September 2007
- ISBN:
- 9780195306750
- eISBN:
- 9780199790203
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195306750.003.0003
- Subject:
- Biology, Evolutionary Biology / Genetics
Natural selection is not the only evolutionary “force” that can alter frequencies of genetic variants; random genetic drift (a sampling process) persistently changes the gene pool of populations, ...
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Natural selection is not the only evolutionary “force” that can alter frequencies of genetic variants; random genetic drift (a sampling process) persistently changes the gene pool of populations, especially in small populations. Moreover, at the molecular level, negative selection is more prevalent than positive selection as deleterious mutations occur much more than do advantageous mutations. Motoo Kimura, a Japanese evolutionary geneticist, expanded on Darwinian evolution and formulated what is now called the neutral theory of molecular evolution. According to Kimura, patterns of molecular evolution are determined primarily by mutation, genetic drift, and negative selection. This chapter discusses the development of the neutral theory, and explains how it lays the foundation to produce tests used to detect positive selection and balancing selection. It also contains a discussion of hypothesis testing.Less
Natural selection is not the only evolutionary “force” that can alter frequencies of genetic variants; random genetic drift (a sampling process) persistently changes the gene pool of populations, especially in small populations. Moreover, at the molecular level, negative selection is more prevalent than positive selection as deleterious mutations occur much more than do advantageous mutations. Motoo Kimura, a Japanese evolutionary geneticist, expanded on Darwinian evolution and formulated what is now called the neutral theory of molecular evolution. According to Kimura, patterns of molecular evolution are determined primarily by mutation, genetic drift, and negative selection. This chapter discusses the development of the neutral theory, and explains how it lays the foundation to produce tests used to detect positive selection and balancing selection. It also contains a discussion of hypothesis testing.
Ian G. Roberts
- Published in print:
- 2005
- Published Online:
- September 2007
- ISBN:
- 9780195168211
- eISBN:
- 9780199788453
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195168211.003.0003
- Subject:
- Linguistics, Syntax and Morphology
This chapter attempts to find the corollaries of the parameter values responsible for the movements identified as underlying VSO order in Chapter 1. A comparison with the behaviour of subject clitics ...
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This chapter attempts to find the corollaries of the parameter values responsible for the movements identified as underlying VSO order in Chapter 1. A comparison with the behaviour of subject clitics in Northern Italian dialects leads to the conclusion that subject-agreement marking in Welsh is a form of incorporated clitic pronoun. This plays a central role in triggering verb-movement, leading to the suggestion that there is no motivation for appealing further to a ‘strong V-feature’. The analysis of the trigger for subject-raising leads to a general account of structural Case-assignment, which, when applied to direct objects, also provides an account of direct-object mutation. Here too, the notion of ‘strong D-feature’ plays no role.Less
This chapter attempts to find the corollaries of the parameter values responsible for the movements identified as underlying VSO order in Chapter 1. A comparison with the behaviour of subject clitics in Northern Italian dialects leads to the conclusion that subject-agreement marking in Welsh is a form of incorporated clitic pronoun. This plays a central role in triggering verb-movement, leading to the suggestion that there is no motivation for appealing further to a ‘strong V-feature’. The analysis of the trigger for subject-raising leads to a general account of structural Case-assignment, which, when applied to direct objects, also provides an account of direct-object mutation. Here too, the notion of ‘strong D-feature’ plays no role.
Julian C. Knight
- Published in print:
- 2009
- Published Online:
- September 2009
- ISBN:
- 9780199227693
- eISBN:
- 9780191711015
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199227693.003.0001
- Subject:
- Biology, Evolutionary Biology / Genetics, Disease Ecology / Epidemiology
Study of genetic variation at the globin genes has provided a series of fundamental insights the nature and extent of genetic diversity and its functional consequences. This chapter provides a primer ...
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Study of genetic variation at the globin genes has provided a series of fundamental insights the nature and extent of genetic diversity and its functional consequences. This chapter provides a primer in human molecular genetics through a systematic review of the elucidation of the genetic basis of haemoglobin S, responsible for sickle cell disease and trait. A review of genetic diversity at or near the globin genes responsible for other structural variants of haemoglobin and the haemoglobinopathies is described. This allows the major classes of genetic variation found in man to be introduced, ranging from fine scale nucleotide diversity to larger scale structural variation. The functional consequences of such diversity are discussed with a number of different examples given. The chapter concludes with a review of the remarkable successes achieved through completion of sequencing the human genome including insights into genetic variation.Less
Study of genetic variation at the globin genes has provided a series of fundamental insights the nature and extent of genetic diversity and its functional consequences. This chapter provides a primer in human molecular genetics through a systematic review of the elucidation of the genetic basis of haemoglobin S, responsible for sickle cell disease and trait. A review of genetic diversity at or near the globin genes responsible for other structural variants of haemoglobin and the haemoglobinopathies is described. This allows the major classes of genetic variation found in man to be introduced, ranging from fine scale nucleotide diversity to larger scale structural variation. The functional consequences of such diversity are discussed with a number of different examples given. The chapter concludes with a review of the remarkable successes achieved through completion of sequencing the human genome including insights into genetic variation.
Steven U. Walkley
- Published in print:
- 2004
- Published Online:
- September 2009
- ISBN:
- 9780198508786
- eISBN:
- 9780191723803
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198508786.003.0012
- Subject:
- Neuroscience, Disorders of the Nervous System
Lysosomal diseases begin quite simply as single gene mutations that affect the function of one protein. This protein may be an enzyme critical in the degradative action of the lysosomal system or in ...
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Lysosomal diseases begin quite simply as single gene mutations that affect the function of one protein. This protein may be an enzyme critical in the degradative action of the lysosomal system or in the processing and/or trafficking of such enzymes to the lysosome. The pathophysiological consequences in brain ultimately play out as an expanding cascade involving multiple substrate accumulation and widespread, but variable, impact on different types of neurones and glia. In some cases these changes may actually appear as regenerative, as seen in the new growth of dendrites and formation of synaptic connections in Tay–Sachs disease, but which more likely lead to inappropriate connections and neuron dysfunction. This chapter discusses the pathogenic cascade in brain; the why, where, and what of storage; the cellular consequences of storage; and functional assessment of brain.Less
Lysosomal diseases begin quite simply as single gene mutations that affect the function of one protein. This protein may be an enzyme critical in the degradative action of the lysosomal system or in the processing and/or trafficking of such enzymes to the lysosome. The pathophysiological consequences in brain ultimately play out as an expanding cascade involving multiple substrate accumulation and widespread, but variable, impact on different types of neurones and glia. In some cases these changes may actually appear as regenerative, as seen in the new growth of dendrites and formation of synaptic connections in Tay–Sachs disease, but which more likely lead to inappropriate connections and neuron dysfunction. This chapter discusses the pathogenic cascade in brain; the why, where, and what of storage; the cellular consequences of storage; and functional assessment of brain.
Bryan G. Winchester
- Published in print:
- 2004
- Published Online:
- September 2009
- ISBN:
- 9780198508786
- eISBN:
- 9780191723803
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198508786.003.0004
- Subject:
- Neuroscience, Disorders of the Nervous System
This chapter begins with a discussion of the molecular genetics of lysosomal enzyme deficiencies. It then discusses the relation of mutations to the structure and function of lysosomal enzymes, and ...
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This chapter begins with a discussion of the molecular genetics of lysosomal enzyme deficiencies. It then discusses the relation of mutations to the structure and function of lysosomal enzymes, and genotype/phenotype correlation in groups of neuronal storage disorders.Less
This chapter begins with a discussion of the molecular genetics of lysosomal enzyme deficiencies. It then discusses the relation of mutations to the structure and function of lysosomal enzymes, and genotype/phenotype correlation in groups of neuronal storage disorders.
Ivan Soltesz
- Published in print:
- 2006
- Published Online:
- May 2009
- ISBN:
- 9780195177015
- eISBN:
- 9780199864713
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195177015.003.0006
- Subject:
- Neuroscience, Neuroendocrine and Autonomic, Techniques
This chapter shows that somatic mutations in the brain may be more frequent than previously believed, and they may result in substantial alterations in synaptic functions involved in learning and ...
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This chapter shows that somatic mutations in the brain may be more frequent than previously believed, and they may result in substantial alterations in synaptic functions involved in learning and memory (i.e., they may have behaviorally significant effects even at the whole organism level). Alterations in the expression levels of genes in cortical tissues that are expressed in interneurons and at GABAergic synapses indicate that these complex processes may contribute to age-dependent changes in cell-to-cell variance within interneuronal populations.Less
This chapter shows that somatic mutations in the brain may be more frequent than previously believed, and they may result in substantial alterations in synaptic functions involved in learning and memory (i.e., they may have behaviorally significant effects even at the whole organism level). Alterations in the expression levels of genes in cortical tissues that are expressed in interneurons and at GABAergic synapses indicate that these complex processes may contribute to age-dependent changes in cell-to-cell variance within interneuronal populations.
