Rosalind Franklin is now also widely credited with generating critical X-ray diffraction data that enabled Watson and Crick to piece together the puzzle of the DNA molecule. Briefly, Francis Crick and James Watson are credited with determining the structure of DNA. The story of this discovery has been widely recounted - and the details are beyond the scope of this text. The appreciation of this dates to the the 1950s. Perhaps one of the best known and popular features of the hereditary form of the DNA molecule is that it has a double helical structure. To build some extra context we also need a little bit of empirically determined knowledge. Use these questions as guideposts for organizing your thoughts and try to find matches between the "facts" that you think you might be expected to know and the driving questions. As you go through the reading and lecture materials try to be constantly aware of these and other questions associated with this process. In the following and in lecture we will discuss how the DNA replication is accomplished while keeping in mind some of these driving questions. So one clear problem/statement/question is "how can the cell effectively copy its DNA?" Given the analogy above, some relevant sub-questions of relevance might be: What are the chemical and physical properties that enable DNA to be copied (we're not just building more DNA- we're building an exact copy of its sequence)? With what fidelity must the DNA be copied? What speed must it be copied at? Where does the energy come from for this task and how much is necessary? Where do the "raw materials" come from? How do the molecular machines involved in this process couple the assembly of raw materials and the energy required to build a new DNA molecule together? The list could, of course, go on. If the cell is to replicate - its ultimate goal - a copy of the DNA must be created. Both the human and bacterium do this while typically making few enough mistakes that the subsequent generation remains viable and recognizable. coli cell may take only 20 minutes to divide (including replicating its ~4.5 million base pair genome). With that in mind, it is worth noting that a human cell can take about 24 hours to divide (DNA replication must therefore be a little faster). How fast could you do it? How many mistakes are you likely to make? Do you expect there to be a trade-off between the speed at which you can copy and the accuracy? What type of resources does this process need? How much energy is required? Now imagine copying something 1000x larger! Now imagine yourself copying these texts. The number of letters in these 7 novels are, however, much closer to the number of nucleotides in a typical bacterial genome. Therefore, even all seven volumes of "Harry Potter" have over 1000x fewer letters than our own genomes. If we assume that the length of the average English word is 5 letters, the two literary works are 2.8 million and 5.4 million letters in length, respectively. This work checks in at ~1,080,000 words ( Referenced Statistics on Wikipedia). A second written work many are familiar with are the seven volumes of J.K. Data from Wikipedia estimates that "War and Peace" contains about 560,000 words. For this example we begin by considering Tolstoy's "War and Peace", a novel many people are familiar with for its voluminous nature. By analogy we can then compare it to another written document. To get a better idea of what that number means, imagine that our DNA is a set of written instructions for constructing one of us. Six point five billion looks like this: 6,500,000,000. if you count the DNA inherited from both parents).
#Dna molecule sugar phosphate backbone and nucleotides full
The human genome consists of roughly 6.5 billion base pairs of DNA if one considers the full diploid genome (i.e. Let us first briefly consider the scope of the problem by way of a literary analogy. In this module we discuss the replication of DNA - one of the key requirements for a living system to reproduce or, in a multicellular system, to grow.
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