On translation , mRNA produce a polypeptide chain , which contains 50 amino acids. if `26^( th)` codon of mRNA UUU mutated and changed to UUC , then the polypeptide chain will be

Options

A. Completely changed
B. Partially changed
C. Not changed
D. only one amino acid changed

Answer

To solve the question, we need to analyze the effect of the mutation of the 26th codon of mRNA from UUU to UUC on the resulting polypeptide chain. Here’s a step-by-step breakdown:

### Step 1: Understand the Codon
- The original codon is UUU. In the genetic code, UUU codes for the amino acid phenylalanine (Phe).
- The mutated codon is UUC. According to the genetic code, UUC also codes for phenylalanine (Phe).

**Hint:** Look up the genetic code table to see which amino acids correspond to which codons.

### Step 2: Identify the Type of Mutation
- Since both UUU and UUC code for the same amino acid (phenylalanine), this type of mutation is known as a **silent mutation**. Silent mutations do not change the amino acid sequence of the protein.

**Hint:** Remember that mutations can be classified as silent, missense, or nonsense based on their effect on the protein.

### Step 3: Determine the Effect on the Polypeptide Chain
- Since the 26th codon change from UUU to UUC does not alter the amino acid being incorporated into the polypeptide chain, the overall sequence of the polypeptide remains unchanged.

**Hint:** Consider how changes in codons affect the resulting amino acids and the overall protein structure.

### Step 4: Conclusion
- The polypeptide chain will remain unchanged despite the mutation in the codon.

**Final Answer:** The polypeptide chain will **not change**.

### Summary of Steps:
1. Identify the original and mutated codons.
2. Determine the amino acids coded by both codons.
3. Classify the mutation type (silent mutation).
4. Conclude the effect on the polypeptide chain.