The number of gene copies produced by PCR can be one billion within few hours by repeating the process for

Options

A. 20 times
B. 30 times
C. 40 times
D. 50 times

Answer

**Step-by-Step Solution:**

1. **Understanding PCR (Polymerase Chain Reaction):**
- PCR is a technique used to amplify a specific DNA segment, creating millions of copies of that segment in a short amount of time. It is an in vitro method, meaning it occurs outside of a living organism.

2. **Process of PCR:**
- PCR involves three main steps:
- **Denaturation:** The double-stranded DNA is heated to separate it into two single strands.
- **Annealing:** Short DNA primers bind to the specific sequences on the single-stranded DNA, providing a starting point for DNA synthesis.
- **Extension:** DNA polymerase adds nucleotides to the primers, synthesizing new strands of DNA.

3. **Cycle Repetition:**
- Each cycle of PCR doubles the amount of DNA.
- After one cycle, you have 2 copies of the DNA.
- After two cycles, you have 4 copies, and this doubling continues with each cycle.

4. **Calculating Copies:**
- The formula for the number of copies after n cycles is given by:
\[ \text{Number of copies} = 2^n \]
- To find out how many cycles are needed to reach 1 billion copies, we set up the equation:
\[ 2^n = 1,000,000,000 \]

5. **Finding n:**
- To solve for n, we can take the logarithm:
\[ n = \log_2(1,000,000,000) \]
- Calculating this gives approximately:
\[ n \approx 29.9 \]
- Since n must be a whole number, we round up to 30.

6. **Conclusion:**
- Therefore, to produce approximately 1 billion copies of a gene, the PCR process needs to be repeated about 30 times.

**Final Answer:**
The number of gene copies produced by PCR can be one billion within a few hours by repeating the process approximately 30 times.

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