Which of the following is not true of an anticodon ?

Answer

To determine which statement about an anticodon is not true, let's analyze the options provided step by step.

### Step 1: Understand what an anticodon is.
An anticodon is a sequence of three nucleotides found on a tRNA (transfer RNA) molecule. It is complementary to a corresponding codon on mRNA (messenger RNA) during protein synthesis.

### Step 2: Analyze the options.
1. **Option 1: It is the basic unit of the genetic code.**
- This statement is incorrect. The basic unit of the genetic code is the codon, which consists of three nucleotides. Anticodons are not the basic unit; they are complementary to codons.

2. **Option 2: Anticodons are present on tRNA molecules.**
- This statement is true. Anticodons are indeed located on tRNA molecules, where they play a crucial role in translation.

3. **Option 3: It may pair with more than one codon.**
- This statement is also true. Due to the wobble hypothesis, some anticodons can pair with multiple codons, especially when the first base of the codon is a specific nucleotide like inosine.

### Step 3: Conclusion
The statement that is not true about an anticodon is **Option 1: It is the basic unit of the genetic code.**

### Summary of the Solution
- Anticodons are not the basic unit of genetic code; that role belongs to codons.
- Anticodons are found on tRNA and can pair with more than one codon.