The numberof punctuation condons in a genetic code are

Options

A. `2+3=5`
B. `1+3=4`
C. `1+1=2`
D. `3`

Answer

To solve the question regarding the number of punctuation codons in a genetic code, we can break it down step by step.

### Step-by-Step Solution:

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

2. **Total Codons**:
- In the genetic code, there are a total of 64 codons. This is derived from the fact that there are four nucleotides (A, U, C, G) and each codon consists of three nucleotides (4^3 = 64).

3. **Identify Punctuation Codons**:
- Punctuation codons are those that signal the start and stop of protein synthesis.
- There is **1 start codon** and **3 stop codons**.

4. **List the Punctuation Codons**:
- The **start codon** is AUG, which codes for Methionine.
- The **stop codons** are UAA, UAG, and UGA.

5. **Calculate the Total Number of Punctuation Codons**:
- Total punctuation codons = 1 (start) + 3 (stop) = 4.

6. **Select the Correct Option**:
- Among the given options:
- 2 + 3 = 5 (incorrect)
- 1 + 3 = 4 (correct)
- 1 + 1 = 2 (incorrect)
- 3 (incorrect)
- Therefore, the correct answer is **1 + 3 = 4**.

### Final Answer:
The number of punctuation codons in a genetic code is **4**.

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