A PCR reaction starts with 5 copies of a target DNA fragment. Assuming 100 % efficiency (each cycle doubles the number of copies), how many DNA molecules are present after 30 cycles? Express the answer in scientific notation.
Answer
copies (approximately)
The correct answer is copies (approximately) — Round to two decimal places in scientific notation: 5.37×10^9 copies.
Step-by-step solution
- Each PCR cycle doubles the number of copies, so after n cycles the total copies = initial copies × 2^n.
- Calculate 2^30. Using known values, 2^10 = 1.024×10^3, 2^20 = (2^10)^2 ≈ 1.0486×10^6, 2^30 = 2^20 × 2^10 ≈ 1.0737×10^9.
- Multiply by the initial 5 copies: 5 × 1.0737×10^9 ≈ 5.3685×10^9 copies.
- Round to two decimal places in scientific notation: 5.37×10^9 copies.
Common mistake: Forgetting to multiply by the initial number of copies
Concept tested: PCR amplification calculation
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