Chapter 17, Problem 1Q

The theoretical amplification accomplished by n cycles of PCR is 2n. Starting from a single DNA segment, how much amplification would you expect to see after 20 cycles of PCR? After 30 cycles?

Summary Introduction

To determine: The amplification of a single DNA segment after 20 cycles of PCR.

Introduction: PCR, also known as, Polymerase Chain Reaction is a DNA amplification technique, which rapidly amplifies and separates DNA segments that are present in small amounts. PCR is used in DNA fingerprinting, DNA sequencing, and forensic sciences. Enzyme DNA polymerase is used in the process of PCR. The enzyme used is heat stable as PCR follows thermal cycling.

Explanation of Solution

The first step of PCR is to identify the DNA segment to be amplified. A single-stranded DNA primer complementary to the target segment is synthesized. Taq polymerase which is a thermostable DNA polymerase is added to catalyze the synthesis of the complementary DNA strand and various amplification cycles are performed to get the desired result.

The general formula for DNA amplification for n number of cycles is 2ⁿ.

The result of the amplification of a single segment after 20 cycles will be as follows:

${\text{2}}^{\text{20}}\text{=1,048,576}$

Therefore, after 20 cycles a single DNA segment will be amplified to millions of copies.

Summary Introduction

To determine: The amplification of a single DNA segment after 30 cycles of PCR.

Introduction: PCR, also known as, Polymerase Chain Reaction is a DNA amplification technique, which rapidly amplifies and separates DNA segments that are present in small amounts. PCR is used in DNA fingerprinting, DNA sequencing, and forensic sciences. Enzyme DNA polymerase is used in the process of PCR. The enzyme used is heat stable as PCR follows thermal cycling.

Explanation of Solution

PCR begins with the identification of the DNA segment to be amplified and is followed by the synthesis of a single-stranded artificial primer complementary to the DNA segment which needs to be amplified. DNA polymerase called Taq polymerase is then added to add nucleotide sequences and synthesize the complementary strand. This process is repeated over n number of cycles in order to achieve the desired results.

The amount of copies produced after n number of cycles is given by the formula 2ⁿ.

The result of the amplification of a single segment after 30 cycles will be as follows:

${\text{2}}^{\text{30}}\text{=1,073,741,824}$

Therefore, after 30 cycles a single DNA segment will be amplified to billions of copies.