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During PCR, a 250‑bp fragment is amplified from a single copy template. If each cycle increases the number of copies by 80 % (i.e., each existing copy produces 0.8 additional copies), how many copies will be present after 25 cycles? Round to the nearest whole number.

medium 2 marks Class 12 · Biology · Molecular Basis of Inheritance
Answer
≈ 2.4 × 10^6 copies

The correct answer is ≈ 2.4 × 10^6 copies — Round to the nearest whole number: 2,400,000 copies.

Step-by-step solution

  1. Define the growth factor per cycle as 1 + 0.8 = 1.8.
  2. Set the number of cycles, n = 25.
  3. Calculate the number of copies after n cycles: 1 × (1.8)^25.
  4. Compute (1.8)^25 ≈ 2.4 × 10^6.
  5. Round to the nearest whole number: 2,400,000 copies.
Common mistake: Using 0.8^25 instead of (1+0.8)^25

Concept tested: PCR amplification kinetics

Published · How this solution was prepared and checked

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