DNA vs RNA--some Organic Chemistry

The main difference between DNA and RNA is the sugar present in the molecules. While the sugar present in a RNA molecule is ribose, the sugar present in a molecule of DNA is deoxyribose. Deoxyribose is the same as ribose, except that Deoxyribose has one more OH. DNA does not exist as a single molecule, but instead as a tightly-associated pair of molecules. These two long strands entwine in the shape of a double helix. This arrangement of DNA strands is called antiparallel. The asymmetric ends of DNA strands are referred to as the 5′ (five prime) and 3′ (three prime) ends. The 5' end lines up with 3' and vice versa. The four bases found in DNA are adenine (A), cytosine (C), guanine (G) and thymine (T). A fifth pyrimidine base, called uracil (U), usually takes the place of thymine in RNA and differs from thymine by lacking a methyl group on its ring. Below are a couple of pictures that show the compositional difference between deoxyribose and ribose and between T and U..

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