Wobble base pair - which terminate translation by binding...

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Wobble base pair In molecular biology , a wobble base pair is a non- Watson-Crick base pairing between two nucleotides in RNA molecules. The four main wobble base pairs are guanine - uracil , inosine - uracil , inosine - adenine , and inosine - cytosine (G-U, I-U, I-A and I-C). The thermodynamic stability of a wobble base pair is comparable to that of a Watson-Crick base pair. Wobble base pairs are fundamental in RNA secondary structure and are critical for the proper translation of the genetic code . In the genetic code , there are 43 = 64 possible codons (tri- nucleotide sequences). For translation , each of these codons requires a tRNA molecule with a complementary anticodon . If each tRNA molecule paired with its complementary mRNA codon using canonical Watson-Crick base pairing, then 64 types (species) of tRNA molecule would be required. In the standard genetic code, three of these 64 codons are stop codons,
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Unformatted text preview: which terminate translation by binding to release factors rather than tRNA molecules, so canonical pairing would require 61 species of tRNA. Since most organisms have fewer than 45 species of tRNA, [1] some tRNA species must pair with more than one codon. In 1966, Francis Crick proposed the Wobble hypothesis to account for this. He postulated that the 5' base on the anticodon, which binds to the 3' base on the mRNA , was not as spatially confined as the other two bases, and could, thus, have non-standard base pairing. [2] As an example, yeast tRNA Phe has the anticodon 5'-GmAA-3' and can recognize the codons 5'-UUC-3' and 5'-UUU-3'. It is, therefore, possible for non-WatsonCrick base pairing to occur at the third codon position, i.e., the 3' nucleotide of the mRNA codon and the 5' nucleotide of the tRNA anticodon. [3]...
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This note was uploaded on 10/13/2011 for the course NS 3200 at Cornell University (Engineering School).

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