According to the genetic code, the mRNA codons UGU and UGC code for the amino acid cysteine, the mRNA codon UGA is a stop codon, and the mRNA codon UGG codes for the amino acid tryptophan. What would a mutation in the second base of the codon UGA likely mean for the resulting protein? (SC.912.L.16.3)

Question

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1 point
The resulting protein would most likely be unaffected.
The resulting protein would most likely be unusually long.
The resulting protein would most likely be unusually short.
The resulting protein would most likely differ by one amino acid.

Answer 1

A mutation in the second base of the codon UGA (which is a stop codon) would change it to UAA or UGA (the possible variations being UGA originally). If we consider a specific change, for example, changing UGA to UGC, the new codon now codes for cysteine instead of signaling the end of translation. This would mean that translation would continue beyond where it normally would have stopped.

Therefore, if UGA mutates and results in a codon that codes for an amino acid instead of being a stop codon, the resulting protein would most likely be unusually long because translation would continue until a new stop codon is reached.

The correct answer would be: The resulting protein would most likely be unusually long.