A sequence of three DNA bases that codes for an amino acid is called

• A. Codon (triplet)
• B. Allele
• C. Autosome
• D. Diploid

Answer: (A)

The key idea is that a sequence of three nucleotides encodes one amino acid. This three-base unit is called a codon. Codons are read during protein synthesis, with each codon guiding the addition of a specific amino acid to the growing protein chain. The reason this fits best is that only a codon describes a precise three-base sequence that determines which amino acid is added; three bases are required to cover the variety of amino acids, given there are four bases. The other terms refer to different genetic concepts: an allele is a version of a gene, an autosome is a non-sex chromosome, and diploid means having two complete chromosome sets.