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). 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. Finally, the DNA double helix has the strong sugar-phosphate backbone on the outside with the bases on the inside, making the molecule stable and protecting the vital coding bases from damage.\) The bases are held together by hydrogen bonds, numerous enough to have a strong cumulative effect on the stability of the DNA molecule as a whole, but weak individually so that they can be broken and DNA can be 'unzipped' easily for replication. Complimentary base pairing means that a larger purine always binds to a smaller pyramidine, keeping a constant distance between the two DNA backbones and resulting in parallel polynucleotide chains. The two strands are thus opposite and complimentary to each other, with sequence of the bases allowing DNA to carry coded information used for protein synthesis. Complimentary base pairing also functions to enable accurate DNA replication, as once the two strands are spearated, complimentary base pairing will reproduce an identical copy of the DNA moelcule. The bases within DNA undergo complimentary base pairing with cytosine forming three hydrogen bonds to guanine, and adenine forming two hydrogen bonds to thymine. This structure enables DNA to coil so that the long molecule is compact and lots of information can be stored in a small space. DNA winds into a double helix, with hydrogen bonding between the bases of each strand like the rungs of a ladder. These bases can be divided into the pyrimidines, cytosine and thymine and the purines, adenine and guanine. As well as a pentose monosaccharide and negatively charged phosphate group, each nucleotide wihtin the chain has one of the four nitrogenous bases within its structure. Each polynucleotide strand has a 5' end and a 3' end, and the two run antiparallel (in opposite directions) within DNA. This forms a very strong sugar-phosphate backbone which contributes to the stability of DNA. This type of bond is a covalent link between the phosphate at the 5' carbon of the pentose sugar of one nucleotide, and the hydroxyl group at the 3' postion of another nucleotide. Nucleic acids are polymers made up of many nucleotide monomers linked together by phosphodiester bonds. DNA is made up of two nucleic acid strands joined by hydrogen bonding.
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