If there are 99 bases in an mRNA that codes for a protein with 33 amino acids and the base at position 30 undergo nonsense mutation , then what will be the length of polypeptide formed ?

Options

A. 11 amino acid long
B. 30 amino acid long
C. 9 amino acid long
D. 29 amino acid long

Answer

To solve the problem, we need to follow these steps:

### Step 1: Understand the given information
We have an mRNA sequence that is 99 bases long and codes for a protein with 33 amino acids. A mutation occurs at the 30th base, which is a nonsense mutation.

**Hint:** Nonsense mutations introduce a premature stop codon in the sequence, which can truncate the resulting protein.

### Step 2: Determine the number of codons
Since each codon consists of 3 nucleotide bases, we can calculate the total number of codons that can be formed from the first 30 bases.

**Calculation:**
- Total bases = 30
- Codons = Total bases / 3 = 30 / 3 = 10 codons

**Hint:** Remember that each codon corresponds to one amino acid.

### Step 3: Identify the effect of the nonsense mutation
The mutation at the 30th base results in a nonsense mutation, which means that the 10th codon will be a stop codon. This will terminate the translation process.

**Hint:** A stop codon signals the end of polypeptide synthesis, meaning no further amino acids will be added after this point.

### Step 4: Calculate the number of amino acids in the polypeptide
Since the 10th codon is a stop codon, it does not code for any amino acid. Therefore, only the first 9 codons will contribute to the formation of amino acids.

**Calculation:**
- Amino acids coded = 10 codons - 1 stop codon = 9 amino acids

**Hint:** The number of amino acids formed is equal to the number of codons before the stop codon.

### Step 5: Conclusion
The length of the polypeptide formed will be 9 amino acids long.

**Final Answer:** The length of the polypeptide formed will be **C - 9 amino acids long**.