Units of Inheritance

3 Key excerpts on "Units of Inheritance"

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  eBook - PDF

  Karp's Cell and Molecular Biology

  • Gerald Karp, Janet Iwasa, Wallace Marshall(Authors)
  • 2021(Publication Date)
  • Wiley

    (Publisher)

  434 CHAPTER 10 The Nature of the Gene and the Genome 10.1 The Concept of a Gene as a Unit of Inheritance Our concept of the gene has undergone a remarkable evolution as biologists have learned more and more about the nature of inheritance. The earliest studies revealed genes to be discrete factors that were retained throughout the life of an organism and then passed on to each of its progeny. Over the following century, these hereditary factors were shown to reside on chro- mosomes and to consist of DNA, a macromolecule with extraor- dinary properties. Figure 10.1 provides an overview of some of the early milestones along this remarkable journey of discov- ery, capped by the description of the double helical structure of DNA in 1953. In the decades that followed this turning point, a major branch of molecular biology began to focus on the genome, the collective body of genetic information that is pres- ent in a species. A genome contains all of the genes required to “build” a particular organism. During the past decade or so, col- laborations by laboratories around the world have uncovered the complete nucleotide sequences of many different genomes, including that of our own species and the chimpanzee, our clos- est living relative. For the first time in human history, we have the means to reconstruct the genetic path of human evolution by comparing the corresponding regions of the genome in related organisms. We can learn which regions of our genome have been duplicated and which have been lost since our split from a common ancestor; we can observe which nucleotides in a particular gene or regulatory region have undergone change and which have remained constant; most importantly, we can infer which parts of our genome have been subject to natural selection and which have been free to drift randomly as time has passed.

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  Karp's Cell and Molecular Biology

  Concepts and Experiments

  • Gerald Karp, Janet Iwasa, Wallace Marshall(Authors)
  • 2016(Publication Date)
  • Wiley

    (Publisher)

  He sent Bea’s DNA off to have key members of the pathway sequenced and compared the returned sequences with those in the recently published human genome. Finding nothing, he expanded his search, enlisting the help of experts in academia and industry. The Nature of the Gene and the Genome 10.1 The Concept of a Gene as a Unit of Inheritance 10.2 The Discovery of Chromosomes 10.3 Chromosomes as the Carriers of Genetic Information 10.4 Genetic Analysis in Drosophila 10.5 The Structure of DNA 10.6 EXPERIMENTAL PATHWAYS: The Chemical Nature of the Gene 10.7 DNA Supercoiling 10.8 The Complexity of the Genome 10.9 THE HUMAN PERSPECTIVE: Diseases That Result from Expansion of Trinucleotide Repeats 10.10 The Stability of the Genome: Duplication 10.11 The Dynamic Nature of the Genome: “Jumping Genes” 10.12 Sequencing Genomes: The Footprints of Biological Evolution 10.13 Comparative Genomics: “If It’s Conserved, It Must Be Important” 10.14 The Genetic Basis of “Being Human” 10.15 Genetic Variation within the Human Species Population 10.16 THE HUMAN PERSPECTIVE: Application of Genomic Analyses to Medicine C H A P T E R O U T L I N E SOURCE: Courtesy of Leah Fasten Photography 366 10.1 • The Concept of a Gene as a Unit of Inheritance 367 10.1 The Concept of a Gene as a Unit of Inheritance Our concept of the gene has undergone a remarkable evolution as biologists have learned more and more about the nature of inherit- ance. The earliest studies revealed genes to be discrete factors that were retained throughout the life of an organism and then passed on to each of its progeny. Over the following century, these hereditary factors were shown to reside on chromosomes and to consist of DNA, a macromolecule with extraordinary properties. FIGURE 10.1 provides an overview of some of the early milestones along this remarkable journey of discovery, capped by the description of the double helical structure of DNA in 1953.

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  eBook - ePub

  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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