A triplet of nucleotides is called a...

• A. Anticodon
• B. Nucleotide
• C. Genome
• D. Codon

Answer: (D)

Codons are three-nucleotide units that specify which amino acid should be added during protein synthesis or signal a stop. In translation, the ribosome reads mRNA in these three-base words, and each codon corresponds to one amino acid (or a termination signal). There are 64 possible codons formed from four nucleotides taken three at a time, which is why the code can specify all 20 amino acids with some codons mapping to the same amino acid. The partner on tRNA that recognizes a codon is the anticodon, a complementary three-base sequence, but the anticodon itself is not the codon. A nucleotide is a single base, and a genome is the entire collection of genetic material. Thus, the triplet of nucleotides used to encode amino acids in translation is a codon.