If DNA codons are ATG GAA, insertion of thymine after the first codon results in,

Options

A. non-sense mutation
B. mis-sense mutation
C. frameshift mutation
D. silent mutation

Explanation

**Step-by-Step Solution:**

1. **Identify the Original Codons:**
The original DNA codons provided are:
- First codon: ATG
- Second codon: GAA

2. **Insert Thymine:**
We need to insert a thymine (T) after the first codon (ATG). The new sequence will be:
- ATG T GAA

3. **Determine the New Codons:**
After inserting thymine, the sequence can be grouped into codons:
- First codon: ATG
- Second codon: TGA (which is formed by the insertion)
- Third codon: A (incomplete codon, but for the sake of understanding, we can consider it as part of the next codon)

4. **Analyze the New Codons:**
- The codon TGA is known as a stop codon.
- Stop codons signal the termination of protein synthesis.

5. **Identify the Type of Mutation:**
Since the insertion of thymine resulted in the formation of a stop codon (TGA), this mutation leads to premature termination of translation. This type of mutation is classified as a **nonsense mutation** because it introduces a stop codon where there was previously a codon that would code for an amino acid.

6. **Conclusion:**
The insertion of thymine after the first codon (ATG) results in a nonsense mutation due to the formation of the stop codon TGA.

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