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¿Qué podemos esperar del concepto molecular de gen?
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What are genes? What do genes do? These seemingly simple questions are in fact challenging to answer accurately. As a result, there are widespread misunderstandings and over-simplistic answers, which lead to common conceptions widely portrayed in the media, such as the existence of a gene 'for' a particular characteristic or disease. In reality, the DNA we inherit interacts continuously with the environment and functions differently as we age. What our parents hand down to us is just the beginning of our life story. This comprehensive book analyses and explains the gene concept, combining philosophical, historical, psychological and educational perspectives with current research in genetics and genomics. It summarises what we currently know and do not know about genes and the potential impact of genetics on all our lives. Making Sense of Genes is an accessible but rigorous introduction to contemporary genetics concepts for non-experts, undergraduate students, teachers and healthcare professionals.
The concept of the gene is and has always been a continuously evolving one. In order to provide a structure for understanding the concept, its history is divided into classical, neoclassical, and modern periods. The classical view prevailed into the 1930s, and conceived the gene as an indivisible unit of genetic transmission, recombination, mutation, and function. The discovery of intragenic recombination in the early 1940s and the establishment of DNA as the physical basis of inheritance led to the neoclassical concept of the gene, which prevailed until the 1970s. In this view the gene (or cistron, as it was called then) was subdivided into its constituent parts, mutons and recons, identified as nucleotides. Each cistron was believed to be responsible for the synthesis of a single mRNA and hence for one polypeptide. This colinearity hypothesis prevailed from 1955 to the 1970s. Starting from the early 1970s, DNA technologies have led to the modern period of gene conceptualization, wherein none of the classical or neoclassical criteria are sufficient to define a gene. Modern discoveries include those of repeated genes, split genes and alternative splicing, assembled genes, overlapping genes, transposable genes, complex promoters, multiple polyadenylation sites, polyprotein genes, editing of the primary transcript, and nested genes. We are currently left with a rather abstract, open, and generalized concept of the gene, even though our comprehension of the structure and organization of the genetic material has greatly increased.
Modifications of RNA affect its function and stability. RNA editing is unique among these modifications because it not only alters the cellular fate of RNA molecules but also alters their sequence relative to the genome. The most common type of RNA editing is A-to-I editing by double-stranded RNA-specific adenosine deaminase (ADAR) enzymes. Recent transcriptomic studies have identified a number of 'recoding' sites at which A-to-I editing results in non-synonymous substitutions in protein-coding sequences. Many of these recoding sites are conserved within (but not usually across) lineages, are under positive selection and have functional and evolutionary importance. However, systematic mapping of the editome across the animal kingdom has revealed that most A-to-I editing sites are located within mobile elements in non-coding parts of the genome. Editing of these non-coding sites is thought to have a critical role in protecting against activation of innate immunity by self-transcripts. Both recoding and non-coding events have implications for genome evolution and, when deregulated, may lead to disease. Finally, ADARs are now being adapted for RNA engineering purposes.
BIOLOGY has evidently borrowed the terms “heredity” and “inheritance” from everyday language, in which the meaning of these words is the “transmission” of money or things, rights or duties—or even ideas and knowledge —from one person to another or to some others: the “heirs” or “inheritors.”
Philosophers and historians of biology have argued that genes are conceptualized differently in different fields of biology and that these differences influence both the conduct of research and the interpretation of research by audiences outside the field in which the research was conducted. In this paper we report the results of a questionnaire study of how genes are conceptualized by biological scientists at the University of Sydney, Australia. The results provide tentative support for some hypotheses about conceptual differences between different fields of biological research.
Genome Analysis and Developmental Biology: The Nematode Caenorhabditis elegans as a Model System
- Thomas Bürglin
Bürglin, Thomas. (2006). Genome Analysis and Developmental Biology: The Nematode Caenorhabditis elegans as a
Model System. En Neumann-Held, Eva y Rehmann-Sutter,
Christoph. Genes in Development. Re-reading the Molecular
Paradigm, pp. 15-38. Durham: Duke University Press.
On Protein Synthesis
- Francis Crick
Crick, Francis. (1958). On Protein Synthesis. Symposium of the
Society of Experimental Biology 12: 138-163.
Genetic Analysis. A History of Genetic Thinking
- Raphael Falk
Falk, Raphael. (2009). Genetic Analysis. A History of Genetic
Thinking. Cambridge: Cambridge University Press.