9. During transcription the DNA base sequence is transcribed into a complimentary mRNA sequence. A codon table like the one shown below lists the amino acids coded for by particular triads of mRNA bases. A segment of DNA has undergone a mutation in which one nucleotide has been changed. The original sequence was ACG and the new sequence is ACA. Use the codon table to determine whether or not this mutation will cause a change in the phenotype of the organism.

Question

(SC.912.L.16.3)
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1 point
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Yes, the phenotype of the organism would change because a new amino acid will be coded for.
Yes, the phenotype of the organism would change because any change in the DNA sequence will cause a change in phenotype.
Even though the DNA sequence changed, the sequence still codes for the same amino acid, so no change in phenotype will occur.
It is impossible to determine if a change in phenotype will occur using only the DNA sequence.

Answer 1

To determine whether the mutation from ACG to ACA changes the phenotype of the organism, we need to examine the mRNA codons that correspond to these DNA sequences.

1. The original DNA sequence: ACG

   • When transcribed to mRNA, this becomes UGC.
   • According to the codon table, UGC codes for the amino acid Cysteine (Cys).

2. The mutated DNA sequence: ACA

   • When transcribed to mRNA, this becomes UGU.
   • According to the codon table, UGU codes for the amino acid Serine (Ser).

Since the original codon (UGC) codes for Cysteine, and the mutated codon (UGU) codes for Serine, there is a change in the coded amino acid due to this mutation.

Therefore, the correct statement is:

Yes, the phenotype of the organism would change because a new amino acid will be coded for.