A stop codon will always have a

Options

A. uracil nucleotide at is 5' end
B. adenine nucleotide at is 5' end
C. uracil nucleotide at is 3' end
D. adenine nucleotide at is 3' end

Answer

To solve the question "A stop codon will always have a...", we need to understand what a stop codon is and its characteristics.

### Step-by-Step Solution:

1. **Definition of Stop Codons**:
- Stop codons are specific sequences of nucleotides in mRNA that signal the end of protein synthesis (translation). The three stop codons are UAG, UAA, and UGA.

2. **Understanding Codon Structure**:
- Codons are made up of three nucleotides. In the context of mRNA, these nucleotides can be adenine (A), uracil (U), cytosine (C), or guanine (G).

3. **Identifying the Nucleotides in Stop Codons**:
- Each of the stop codons contains uracil (U) as one of its nucleotides. Specifically, all stop codons have uracil at least once in their sequence.

4. **Analyzing the Options**:
- The question asks what a stop codon will always have. Given the nature of stop codons, we can conclude that they will always have uracil (U) in their structure.

5. **Conclusion**:
- Therefore, the correct answer to the question is that a stop codon will always have a uracil nucleotide.

### Final Answer:
A stop codon will always have a uracil nucleotide.