Out of 64 codons, how many of them code for stop signal?

Options

A. 3
B. 2
C. 5
D. 4

Answer

To solve the question "Out of 64 codons, how many of them code for stop signal?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand Codons**: Codons are sequences of three nucleotide bases in mRNA that correspond to specific amino acids or signals during protein synthesis.

2. **Total Codons**: There are a total of 64 possible codons in the genetic code. This is derived from the fact that there are four different nucleotide bases (adenine, cytosine, guanine, and uracil in RNA) and codons are made up of three bases (4^3 = 64).

3. **Identify Stop Codons**: Among these 64 codons, certain codons do not code for any amino acids but instead serve as stop signals to terminate protein synthesis.

4. **Count the Stop Codons**: There are three specific codons that function as stop signals:
- UAA (Amber)
- UAG (Ochre)
- UGA (Opal)

5. **Conclusion**: Therefore, out of the 64 codons, 3 codons code for stop signals.

### Final Answer:
**3 codons code for stop signals.**

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