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Why can fewer than 61 types of transfer RNA read the 61 amino-acid codons?

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Diagram of a DNA polynucleotide chain showing linked deoxyribose sugars, phosphate groups, and nitrogenous bases (adenine, guanine, cytosine, thymine), with an inset comparing ribose and uracil in RNA. — Nucleic acid A portion of the polynucleotide chain of deoxyribonucleic acid (DNA), with an inset showing the corresponding pentose sugar and pyrimidine base in ribonucleic acid (RNA).

The 61 codons that specify amino acids can be read by fewer than 61 distinct types of transfer RNA (tRNA) because of the degeneracy of the genetic code.

While there are 61 codons used to code for amino acids, many amino acids are specified by more than one codon. Because of this, a single type of tRNA can often recognize and bind to multiple codons that specify the same amino acid. This efficiency allows organisms to translate the full set of codons using a smaller number of tRNA molecules; for example, the bacterium Escherichia coli utilizes only 40 different tRNAs to translate all 61 codons.123

During protein synthesis, the anticodon on the tRNA molecule pairs with the complementary codon on the messenger RNA. The ability of fewer tRNAs to cover all codons is a fundamental aspect of how cells manage the translation process efficiently.143