Let's analyze the question step-by-step to understand the impact of the transcription error.
1. Original mRNA Sequence and Translation:
- The original mRNA sequence is: UUG AUC CAA UGC
- We need to translate each codon in this sequence into its corresponding amino acid using the provided codon table.
[tex]\[
\begin{aligned}
&\text{Codon} && \text{Amino Acid} \\
&\text{UUG} && \text{Leucine} \\
&\text{AUC} && \text{Isoleucine} \\
&\text{CAA} && \text{Glutamine} \\
&\text{UGC} && \text{Cysteine} \\
\end{aligned}
\][/tex]
Therefore, the original sequence translates to: Leucine, Isoleucine, Glutamine, Cysteine.
2. Mutated mRNA Sequence and Translation:
- According to the question, an error causes the last cytosine in the sequence to be replaced with a guanine.
- The mutated mRNA sequence is: UUG AUC CAA UGG
- We need to translate this mutated sequence into its corresponding amino acids using the provided codon table.
[tex]\[
\begin{aligned}
&\text{Codon} && \text{Amino Acid} \\
&\text{UUG} && \text{Leucine} \\
&\text{AUC} && \text{Isoleucine} \\
&\text{CAA} && \text{Glutamine} \\
&\text{UGG} && \text{Tryptophan} \\
\end{aligned}
\][/tex]
Therefore, the mutated sequence translates to: Leucine, Isoleucine, Glutamine, Tryptophan.
3. Prediction Analysis:
- Let's evaluate the predictions provided in the question based on the given analysis:
- Nothing will happen, since the last codon will still correspond to threonine.
- This statement is incorrect because the last codon in the original sequence translates to Cysteine, not Threonine.
- Only three amino acids will be produced instead of four.
- This statement is incorrect because all four amino acids are still produced, but the last one changes.
- The first amino acid in the chain will be glycine instead of arginine.
- This statement is incorrect because the first amino acid remains Leucine.
- The last amino acid in the chain will be tryptophan instead of cysteine.
- This statement is correct because the mutation changes the last codon from UGC (Cysteine) to UGG (Tryptophan).
Hence, the correct prediction is:
The last amino acid in the chain will be tryptophan instead of cysteine.
