. "7 What Is the Information That Defines and Sustains Life?." The Role of Theory in Advancing 21st-Century Biology: Catalyzing Transformative Research. Washington, DC: The National Academies Press, 2008.
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The Role of Theory in Advancing 21st-Century Biology: Catalyzing Transformative Research
Many biological structures or processes can be thought of as carriers of information. From the sequence of a DNA molecule, to sounds, nerve impulses, signaling molecules, or chemical gradients, scientists find it useful to characterize biology in terms of information. From the critical discovery of the “genetic code” as the coupler between DNA sequence and protein synthesis, to the marvelous ability of bees to convey information about the location and quality of resources through dance, it is intuitively appealing to describe the processes and structures of biology in information terms. Throughout this report, there are numerous examples of the representation and transmission of information. Questions that naturally arise about information in biology include these: Is there a common way to think of the biological information in all of these representations? Is there a consistent and useful way to measure biological information so that it can be dealt with in quantitative descriptions of genetics, evolution, molecular processes, and communication between organisms?
In common usage, the word “information” conveys many different notions. It is often used as a synonym for “data” or knowledge, and in most common language uses it is associated with written or spoken numbers or words. This connection is key to a more scientific use of the term, in that it suggests that information can be represented by numbers or letters or more generally by symbols of any form. Indeed, information must have a representation, whether it is as written symbols, bits in computers, or in macromolecules, cells, sounds, or electrical impulses. The informal use of informational terms is widespread in molecular biology. For example, molecular biology uses words that relate to transfer and processing of information as technical terms for biological processes. The choice of words like code, translation, transcription, messenger, editing, and proofreading reflects how scientists think of these processes. When information is used as the focal concept for thinking about molecular biology, it highlights the sequence properties of the molecules under study, instead of their actual physiochemical forms (Godfrey-Smith, 2007). This prompts a focus on the abstract representational role of these molecules, rather than the nature of the physical processes (e.g., the biochemistry of the translational machinery) that are inevitably required to express the stored information in meaningful form. It is important to think carefully about information at many levels, both below the sequence level in molecular detail and above at higher levels of organization.
INFORMATION IN BIOLOGY
August Weismann appears to have been the first to explicitly use the notion of information transmission in genetics in 1904 when he referred to the transmission of information in heredity (Weismann, 1904). The meta-