Which sequences are stop codons?

Which sequences are stop codons?

• A. UAA, UAG, UGA
• B. AUG
• C. UAA, UAC
• D. UGG

Answer: (A)

Stop codons signal the end of translation. In the genetic code, most codons specify an amino acid, but three special codons do not code for any amino acid and instead recruit release factors to terminate the growing polypeptide chain. The sequences that perform this stop signal are UAA, UAG, and UGA. They are recognized as termination signals rather than as instructions to add an amino acid, so translation ends when one of these appears. It helps to contrast with other codons: AUG is the start codon and codes for methionine, initiating translation, so it is not a stop codon. UAC codes for tyrosine, and UGG codes for tryptophan—neither terminates translation.

Stop codons signal the end of translation. In the genetic code, most codons specify an amino acid, but three special codons do not code for any amino acid and instead recruit release factors to terminate the growing polypeptide chain. The sequences that perform this stop signal are UAA, UAG, and UGA. They are recognized as termination signals rather than as instructions to add an amino acid, so translation ends when one of these appears.

It helps to contrast with other codons: AUG is the start codon and codes for methionine, initiating translation, so it is not a stop codon. UAC codes for tyrosine, and UGG codes for tryptophan—neither terminates translation.