Why T in DNA and U in RNA?

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Why T in DNA and U in RNA?

Postby BioWizard on January 5th, 2018, 1:23 pm 

Interesting biochemistry factoid. If you've ever wondered why Thymine is used in DNA and Uridine in RNA, here's a likely explanation:

Uracil is energetically less expensive to produce than thymine, which may account for its use in RNA.

In DNA, however, uracil is readily produced by chemical degradation of cytosine, so having thymine as the normal base makes detection and repair of such incipient mutations more efficient.

Thus, uracil is appropriate for RNA, where quantity is important but lifespan is not, whereas thymine is appropriate for DNA where maintaining sequence with high fidelity is more critical.

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