What is not true for the genetic code?

Options

A. It is nearly universal
B. It is degenerate
C. It is unambiguous
D. A codon in mRNA is read in a non-contiguous fashion

Answer

To determine which statement is not true for the genetic code, we will analyze each of the provided options based on our understanding of the genetic code.

### Step-by-Step Solution:

1. **Understanding the Genetic Code**:
The genetic code is a set of rules that defines how the sequence of nucleotides in DNA and RNA is translated into amino acids, which are the building blocks of proteins. It consists of codons, which are sequences of three nucleotides.

2. **Reviewing the Properties of the Genetic Code**:
- **Nearly Universal**: The genetic code is nearly universal, meaning it is the same across almost all organisms, from bacteria to humans. This is a true property of the genetic code.
- **Degenerate**: The genetic code is degenerate, which means that a single amino acid can be encoded by more than one codon. This is also a true property of the genetic code.
- **Unambiguous**: The genetic code is unambiguous, meaning that each codon specifies only one amino acid. This is another true property of the genetic code.
- **Non-Contiguous Reading**: The statement that a codon in mRNA is read in a non-contiguous fashion implies that there are breaks or separators between codons. This is not true; codons are read in a contiguous manner without interruptions.

3. **Identifying the Incorrect Statement**:
Based on the analysis:
- Options 1, 2, and 3 are true properties of the genetic code.
- Option 4, which states that a codon in mRNA is read in a non-contiguous fashion, is not true.

### Conclusion:
The statement that is not true for the genetic code is **Option 4: A codon in mRNA is read in a non-contiguous fashion**.

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