Which of the following is not a salient features of genetic code

Options

A. three codons do not code for any amino acids
B. unambiguous and specific
C. code is nondegenerate
D. the codon is read in mRNA in a contiguous fashion

Answer

To determine which of the following is not a salient feature of the genetic code, we will analyze the characteristics of the genetic code step by step.

### Step 1: Understand the Features of Genetic Code
The genetic code has several key features:
1. **Triplet Codons**: Codons are composed of three nucleotides (e.g., AUG).
2. **Non-overlapping**: Codons do not overlap; each codon is read separately.
3. **Non-punctuated**: There are no punctuation marks between codons.
4. **Degenerate**: Multiple codons can code for the same amino acid.
5. **Unambiguous**: Each codon specifies only one amino acid.
6. **Universal**: The genetic code is largely the same across all organisms.
7. **Initiator and Terminator Codons**: Certain codons signal the start (e.g., AUG) or stop (e.g., UAG, UGA) of protein synthesis.

### Step 2: Analyze the Options
Now, let's evaluate the options given in the question:
1. **3 codons do not code for any amino acid**: This refers to stop codons, which do not code for any amino acid, making this a true feature of the genetic code.
2. **Unambiguous and specific**: This is a true feature since each codon corresponds to a specific amino acid.
3. **Codon is non-degenerate**: This statement is incorrect because the genetic code is degenerate, meaning that one amino acid can be coded by multiple codons.
4. **Codon is read in a contiguous fashion**: This is true, as codons are read sequentially without interruptions.

### Step 3: Identify the Incorrect Feature
From the analysis, the statement "Codon is non-degenerate" is not a salient feature of the genetic code because the genetic code is indeed degenerate.

### Conclusion
The correct answer to the question "Which of the following is not a salient feature of genetic code?" is the third option: **Codon is non-degenerate**.

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