Final answer:
In translation, four nucleotides specify 20 amino acids, and there are 64 possible codons because each amino acid is encoded by triplets of nucleotides. With 61 codons for amino acids, and three stop codons, the genetic code demonstrates redundancy and specificity.
Step-by-step explanation:
In translation, four nucleotides specify 20 amino acids, but there are 64 possible codons. This disparity arises because each amino acid is encoded by triplet combinations of the four nucleotides (A, U, G, C) in mRNA. The use of three-nucleotide codons means there are 4³ (4 times 4 times 4) combinations, totaling 64. Of these, three are stop codons which signal the end of protein synthesis, and the remaining 61 represent amino acids.
Notably, since there are more codons than amino acids, redundancy in the genetic code is observed. For instance, multiple codons can specify a single amino acid. The codon AUG is unique because it specifies the amino acid methionine and also serves as the start codon that initiates translation. Conversely, the stop codons (UGA, UAA, and UAG) do not encode an amino acid but instead terminate the translation process. This redundancy and specialized codon usage highlight the genetic code's complexity and sophistication in protein synthesis.