The single stranded DNA of phage `phixx174` has 5400 nucleotides. If average protein contains 200 amino acids, how many different proteins could this phage DNA code?

Options

A. 100
B. 90
C. 9
D. 27

Explanation

To solve the problem of how many different proteins the phage DNA can code for, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the relationship between nucleotides and amino acids**:
- Each amino acid in a protein is coded by a sequence of three nucleotides, known as a codon.

2. **Calculate the total number of codons**:
- Given that the phage has 5400 nucleotides, we can find the number of codons by dividing the total number of nucleotides by 3 (since each codon consists of 3 nucleotides):
\[ \text{Number of codons} = \frac{5400 \text{ nucleotides}}{3} = 1800 \text{ codons} \]

3. **Determine how many codons are needed for one protein**:
- Since an average protein contains 200 amino acids, and each amino acid is coded by one codon, the number of codons required for one protein is:
\[ \text{Codons per protein} = 200 \text{ amino acids} \]

4. **Calculate the number of different proteins that can be formed**:
- To find out how many different proteins can be formed from the total number of codons, we divide the total number of codons by the number of codons needed for one protein:
\[ \text{Number of different proteins} = \frac{1800 \text{ codons}}{200 \text{ codons/protein}} = 9 \text{ proteins} \]

### Final Answer:
The phage DNA can code for **9 different proteins**.

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