Final answer:
Fewer than 61 tRNAs are needed to decode the 61 sense codons due to the wobble hypothesis, which allows some tRNAs to pair with multiple codons. The exact number often ranges from 40 to 50 different tRNAs in eukaryotic cells.
Step-by-step explanation:
The many tRNAs it takes to decode the 61 sense codons is that there is not a one-to-one correspondence between tRNAs and codons. Thanks to the wobble hypothesis, fewer than 61 tRNAs can pair with all 61 sense codons.
In the translation process, tRNAs serve as adaptors that translate the genetic code from RNA language into proteins. While there are 61 sense codons that specify amino acids in a polypeptide chain, the actual number of tRNAs is not equal to the number of sense codons due to the flexibility allowed by the wobble hypothesis. This hypothesis explains that the base at the 5' end of the tRNA anticodon, which pairs with the 3' base of the mRNA codon, can exhibit less stringent pairing rules, thus allowing one tRNA to read multiple codons.
Moreover, the genetic code is degenerate, meaning several codons can code for the same amino acid. Consequently, organisms have evolved tRNAs with anticodons that can base pair with more than one codon through wobble base pairing, enabling a smaller set of tRNAs to accommodate all sense codons required for protein synthesis. Typically, eukaryotic cells have about 40-50 different tRNAs, which is enough to cover all 61 sense codons that encode the 20 amino acids thanks to this wobble base pairing.