A virus with ssDNA is discovered. Its DNA is amplified by running 19 cycles of PCR. How many dsDNA strand will be formed at the end ?
(a) 10
(b) 512
(c) 1024
(d) 102

Options

A. 10
B. 512
C. 1024
D. 102

Answer

To solve the problem, we need to determine how many double-stranded DNA (dsDNA) strands will be formed after running 19 cycles of PCR on a single-stranded DNA (ssDNA) virus.

### Step-by-Step Solution:

1. **Understanding PCR**:
- PCR (Polymerase Chain Reaction) is a method used to amplify DNA. Each cycle of PCR typically doubles the amount of DNA present.

2. **Initial Condition**:
- We start with a single-stranded DNA (ssDNA). In the first cycle of PCR, this ssDNA will be converted into a double-stranded DNA (dsDNA).

3. **Cycles of PCR**:
- In the first cycle, the ssDNA is converted into 1 dsDNA molecule.
- From the second cycle onward, each dsDNA will serve as a template for further amplification.

4. **Calculating the Number of dsDNA after 19 Cycles**:
- The formula for calculating the number of dsDNA strands formed in PCR is generally \(2^n\), where \(n\) is the number of cycles.
- However, since the first cycle is used to convert ssDNA to dsDNA, we effectively have \(19 - 1 = 18\) cycles left for amplification.
- Thus, we need to calculate \(2^{18}\) to find the total number of dsDNA strands formed after the 19 cycles.

5. **Calculating \(2^{18}\)**:
- \(2^{18} = 262144\) dsDNA strands.

6. **Final Count**:
- Since the first cycle was used to create the first dsDNA, we can say that after 19 cycles, we will have \(2^{18} = 262144\) dsDNA strands.

### Conclusion:
The total number of double-stranded DNA strands formed at the end of 19 cycles of PCR is **262144**.

### Answer:
None of the provided options (10, 512, 1024, 102) are correct based on the calculation. The correct answer is **262144**.