Chapter 20, Problem 20.87QP

Interpretation Introduction

Interpretation:

The number of copies of target DNA after 12 cycles of polymerase chain reaction has to be calculated.

Concept Introduction:

Polymerase chain reaction (PCR) is widely used to amplify DNA sequences to produce millions of copies of a specific DNA segment. PCR technique finds applications for specific and rapid diagnosis of infectious diseases.

The various steps involved in PCR technique is as follows:

Stage 1: In the first stage, high temperature $\left(94-98°\text{C}\right)$ is provided so that DNA strands are separated and a single-stranded template gets generated.

Stage 2: In the next step, annealing is done at a temperature of about $50\text{-65 }°\text{C}$ so that primer may bind to the complementary strand on the template generated in stage 1.

Stage 3: In the third stage, two DNA strands obtained after annealing serve as a template for the DNA polymerase, and the enzyme then begins to extend the primers in both directions at about $\text{72 }°\text{C}$.

This cycle is repeated for about 35 times until the target DNA region gets copied.

Each successive cycle of a polymerases chain reaction double the gene as illustrated below: