Group of three bases on DNA or RNA that codes for an amino acid is called what?

• A. Anti-codon
• B. Intron
• C. Exon
• D. Codon

Answer: (D)

A codon is the three-nucleotide unit in the genetic code that specifies an amino acid. In RNA, these triplets are read by the ribosome during translation, and each codon corresponds to a specific amino acid (with some codons serving as stop signals to end protein synthesis). The same idea applies to DNA in the sense that the corresponding three-base sequence (a DNA triplet) carries the genetic code that will be transcribed and then translated. The codon is matched by a tRNA molecule whose anticodon is complementary, bringing the correct amino acid to the growing polypeptide chain. By contrast, an anticodon is the tRNA’s three-base partner, introns are non-coding sequences removed from RNA, and exons are the coding segments retained in the mature mRNA.