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Deoxyribonucleic acid (DNA) is sometimes described as a "blueprint" for development. Although easy to visualize, that view is a damaging oversimplification. A blueprint defines the location of each element in a given structure. In contrast, genetic control of development is much more dynamic. A better description for the role of DNA is as a "recipe for interactions." DNA codes for the assembly of proteins by way of a ribonucleic acid (RNA) intermediate, the messenger RNA (mRNA). But it is the interactions among the resulting proteins, other RNAs like microRNAs, and their feedback influences on the genome that will determine how cells, tissues, organs, and the body as a whole will take on its form and function.
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As the ultimate information resource for biological processes, DNA is essential. But in many ways it is the simplest part of the development puzzle. In 1953, Watson and Crick proposed a model for the structure of DNA that has been confirmed by experiments to test predictions about processes like DNA replication during cell division. But knowing the structure of DNA does not explain how it works. Sequencing the human genome was also not the final answer. Instead, knowing the genome's DNA structure leads to a higher level of questions. How is DNA organized into genes that control the activities of a cell to create individual phenotypes? How do genes influence each other? How do proteins interact with each other to form networks of biochemical change? How do functional pathways and feedback loops influence the organism at a level beyond the simple turning-on of a gene? Answering questions like these is the focus of new fields like genomics, bioinformatics, proteomics, and metabolomics. Furthermore, genes do not work in isolation from their cellular and developmental environment. What roles do environmental variables like temperature play in forming a trait?
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Building from that perspective, we can think of our development as the product of a molecular storm. Storms may be influenced by rules, but the rules are often complex and random events can be influential. Rather than genes providing a simple blueprint, the unfolding of each step in development is actually the result of hundreds, if not thousands, of different molecular interactions. This perspective is introduced here but will be explored in detail in later chapters. DNA is only the beginning.
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Part 1: Background and Systems Integration
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From DNA to Protein: the Central Dogma of Molecular Biology
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A dictionary definition of "dogma" is that it is information presented as an established opinion or an authoritative view, but without significant grounds of support. In that sense, the Central Dogma of Molecular Biology is famously misnamed. The flow of information it describes is extensively supported by experimental evidence. Still, it compactly summarizes the unifying theme of molecular genetics: DNA ↔ RNA → polypeptide (Figure 2-1). The nucleotides that make ...