The1 - amino acid codons are recognized. The...

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The translation process occurs at the ribosome and involves the three major classes of RNA: mRNA, tRNA, and rRNA. This is true for prokaryotes and eukaryotes. Earlier in the semester we talked about the genetic code, about tRNAs and how they are specifically loaded with the correct amino acids and about ribosomes and their two specific subunits. One more important finding: Organisms usually do not contain as many different kinds of tRNAs as there are codons for amino acids (remember: 64 possible combinations for a triplet formed from 4 different bases (4 to the 3). 3 of these combinations are stop codons, but 61 code for amino acids). In E. coli for example there are about 40 different tRNAs for the 20 different amino acids. It turns out that some tRNAs can base pair with more than one codon so all 61
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Unformatted text preview: amino acid codons are recognized. The codon-anticodon base pairing requirements are somewhat less stringent than those for DNA or RNA synthesis. This was first proposed by Francis Crick in 1965 and became known as the wobble hypothesis . Crick proposed that the conformational constraints for codon-anticodon base pairing are less stringent because they do not occur in the context of a double helix which is so easily distorted. For example G-U base pairing can occur in codon-anticodon interaction (Fig. 7.3). Wobbling (the less stringent, unusual base pairing due to conformational relaxation) usually occurs at the third base in a triplet codon (which corresponds to the first base in an anticodon)....
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This document was uploaded on 11/03/2011 for the course BIOLOGY MCB2010 at Broward College.

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