Inheritance

5 Key excerpts on "Inheritance"

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  Human Variation

  Races, Types, and Ethnic Groups

  • Stephen Molnar(Author)
  • 2015(Publication Date)
  • Routledge

    (Publisher)

  chapter

  2

  The Biological Basisfor Human Variation        

  The journey from the discovery of particulate Inheritance to the definition of gene structure has been a long one, occupying most of the last century. From simple observations of Inheritance between generations of easily perceived traits to descriptions of the chemical nature of the gene (DNA), we have witnessed an explosion of biochemical data on cell function and control of metabolic processes. Over this time period, assisted by evermore sophisticated techniques, we are able to view Inheritance at several levels: trait transmission between generations, gene and gene combinations, and the molecular or biochemical structure.

  With our new-found knowledge it is all too easy to forget or even to ignore some of the key landmarks along the road leading to an understanding of the biological basis for human variation. Many of these landmarks are fundamental for comparisons of population diversity, and it is best to refresh our memory from time to time if we are to appreciate the new molecular genetic discoveries and their meanings for human adaptations to our changing environments.

  First, recall that humans share similar modes of reproduction with most other mammals, and Inheritance mechanisms are the same—the combination of certain materials from the germ cells of male and female parents to produce a fertilized egg. These mechanisms of Inheritance are the source of much of the vast diversity seen in the biological world. For many centuries, natural scientists had sought to comprehend and explain this diversity in the transmission of traits between generations. Explanations varied from a description of a “blending” of parental bloodlines, favored by animal husbandry, to a theory of “preformism,” the idea that the individual, in miniature form, existed in either the ovum or sperm awaiting stimulation by fertilization to begin its development. None of these explanations could account for the ranges of individual similarities or differences among offspring and their parents.

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  Extended Heredity

  A New Understanding of Inheritance and Evolution

  • Russell Bonduriansky, Troy Day(Authors)
  • 2018(Publication Date)
  • Princeton University Press

    (Publisher)

  2 Heredity from First Principles The whole subject of Inheritance is wonderful.

  —Charles Darwin, Variation of Animals and Plants under Domestication, 1875

  If there is one property that captures the uniqueness of living things, it is their ability to perpetuate their kind through the production of similar forms—that is, reproduction with heredity.15 In all cellular life-forms (that is, all but the simplest biological entities, such as viruses), biological reproduction also follows a universal pattern that can be said to comprise two basic elements. First, reproduction involves the perpetuation of the cell lineage through an unbroken chain of cell division, such that all cells (including Venter’s chimeric bacteria) come from preexisting cells.16 Second, reproduction involves the duplication and transmission of a DNA sequence, embodied in the famous double helix whose chemical properties encode “instructions” for the synthesis of proteins and the regulation of cellular processes. To us, these two basic elements of the reproductive process imply an inherent duality in the nature of heredity (figure 2.1 ).

  In this chapter, we will attempt to reimagine heredity from first principles. The point of this somewhat quixotic exercise is to walk the reader through the logic of extended heredity and (we hope) make a convincing case for the ideas that we will elaborate upon and apply later in this book. These ideas are not really new. Although, as we will see in chapter 3 , the triumph of Mendelian genetics in the early twentieth century displaced the debate on the nature of heredity to the margins of biology, calls to extend heredity to encompass nongenetic factors alongside genes continued into the 1960s.17 This debate resumed in the 1990s as evidence of Inheritance through epigenetic mechanisms such as the transmission of DNA methylation patterns (that is, the presence or absence of methyl groups bonded to certain DNA bases) began to emerge.18 Yet, scientists being a cautious and conservative tribe, the idea of extended heredity is only now starting to be taken seriously, and the outlines of this new concept are still very much in flux.19

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  Advanced Molecular Biology

  A Concise Reference

  • Richard Twyman(Author)
  • 2018(Publication Date)
  • Garland Science

    (Publisher)

  Box 1.1 ). Mendel’s principles of Inheritance can be summarized as follows.

  (1) The heredity and variation of characters are controlled by factors, now called genes, which occur in pairs. Mendel called these factors Formbildungelementen (form-building elements).

  (2) Contrasting traits are specified by different forms of each gene (different alleles).

  (3) When two dissimilar alleles are present in the same individual (i.e. in a heterozygote), one trait displays dominance over the other: the phenotype associated with one allele (the dominant allele) is expressed at the expense of that of the other (the recessive allele).

  Table 1.1: Definitions of some common terms used in transmission genetics

  Term	Definition
  Allele	Broadly, a variant form of a gene specifying a particular trait. At the molecular level, a sequence variant of a gene (q.v. wild-type allele, mutant allele, polymorphism)
  Character	A biological property of an organism which can be detected or measured
  Character mode	A general type of character, e.g. eye color
  Character trait, trait, variant	A specific type of character, e.g. blue eye color
  Gene	Broadly, a hereditary factor controlling or contributing to the control of a particular character. At the molecular level, a segment of DNA (or RNA in some viruses) which is expressed, i.e. used to synthesize one or more products with particular functions in the cell (q.v. gene, cistron, gene expression)
  (Gene) locus	The position of a gene (or other marker or landmark) on a chromosome or physical or genetic map. A useful term because it allows discussion of genes irrespective of genotype or zygosity
  Genetic	Pertaining to genes. Of characters, heredity and variation arising from the nucleotide sequence of the gene (cf. epigenetic, environmental

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  Molecular Hematology

  • Drew Provan, John Gribben(Authors)
  • 2019(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  Chapter 25 History and development of molecular biology

  Paul Moss

  School of Cancer Sciences, University of Birmingham, Birmingham, UK

  1. Evolution is the central tenet of biology
  2. The understanding of monogenic and polygenic Inheritance
  3. DNA as the conduit of genetic information
  4. The rough guide to the human genome
  5. Experimental techniques and molecular biology
  6. Conclusion
  7. Further reading

  Evolution is the central tenet of biology

  It is 160 years since the publication of On the Origin of Species by Means of Natural Selection (Figure 25.1 a). Darwin's far-reaching insights placed natural variation and adaptation as the prime determinants of population change. Evolution is now recognized as the unifying theme of all biology, including hematology and medicine, and these landmark observations can perhaps be recognized as the initiation of the modern discipline of molecular genetics.

  Figure 25.1

  (a) Charles Darwin. (b) Gregor Mendel. (c) Francis Crick and James Watson. (d) Fred Sanger.

  However, despite his unique vision and imagination, Darwin was never able to understand the nature of genetic Inheritance. It was clear that phenotypic characteristics were passed from one generation to the next, but usually these characteristics were “blended,” so that a combination of tall and short parents would produce a child of medium height. Darwin proposed his own model for heredity which he termed pangenesis, in which cells of the body shed gemmules that collect in the reproductive organs. The concept was that all the tissues in the body thus had some impact on Inheritance, but this concept has clearly been superseded. At this time there was no concept of the distinction between the germline and somatic tissue, and it is therefore not surprising that even brilliant scientists such as Jean-Baptiste de Lamarck believed that acquired phenotypic features could be passed, through reproduction, into the subsequent generation. However, despite his somewhat imperfect conclusions, Lamarck was actually an extremely important figure in evolutionary theory, as he developed the concept that a species can change between

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  Death, Deeds, and Descendents

  Inheritance in Modern America

  • Remi Clignet, Jens Beckert, Brooke Harrington(Authors)
  • 2018(Publication Date)
  • Routledge

    (Publisher)

  mortis causa are associated with the evocation of sharply focused feelings toward particular relatives, toward the behaviors or ideas the latter epitomize, and toward the ideals that such behaviors symbolize. In this sense, Inheritance is the repository of collective memories or values (Lichtman 1982; Hyde 1983). Thus, Inheritance is about specific heritages.

  Interaction among the Genetic, Economic, and Cultural Components of Inheritance

  Heredity, Inheritance, and heritage, as forms of transfer, respectively, of genetic, economic, and cultural capital, interact constantly with one another. Thus, long-term cycles of upward or downward economic mobility have a double effect on the developmental opportunities and constraints of successive generations. Since these cycles affect patterns of exogamous marriages and more specifically the economic, social, and cultural distance separating the respective familial groups of conjugal partners, the same cycles broaden or restrict the genetic pool of the populations under consideration. As such, they modify the limits of the human capital that individuals can acquire.9 Yet these long-term economic forces also influence life-styles, notably with respect to nutrition and health, and thus the actual mobilization of this human capital. In a nutshell, economic growth facilitates the systematic development of human capital but, in turn, interindividual variations in the accumulation of this particular type of asset account for differences in the creation and upkeep of material wealth.

  The preeminence of cultural over other forms of capital comes from the very fact that culture represents both “the rules and the stakes” of the game (Bowles and Gintis 1986:119).10

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