Chapter 13, Problem 19A

Summary Introduction

To determine:

The flowchart for PCR technique.

Introduction:

PCR is polymerase chain reaction. This method is used to make millions copies of the required DNA fragment. In this process, only a small quantity of sample DNA is required, and this small quantity is much enough to study the process in detail.

Explanation of Solution

Steps of PCR are as follows:

Step 1 − Denaturation − More than 90 degrees Celsius of temperature is required to denature the given DNA double stranded strand. The hydrogen bonds in DNA are broken down at such higher temperature.

Step 2 − Annealing − Primers are used in PCR technique. These primers are small and synthetic single strand nucleotides and consist of 20-30 bases only. Primers anneal (bind) to the complementary sequence of denatured DNA. This process occurs ate temperature of 40-65 degrees Celsius.

Step 3 − Extension − This process takes place at 72 degrees Celsius. Here Taq DNA polymerase enzyme is used for the replication of DNA strands. This DNA polymerase is thermally stable. This DNA pol uses dNTPs present in the experiment solution.

Step 4 − End of first PCR cycle − When two identical copies of the sample DNA are formed, then their 5’ ends are defined by the primer, but their 3’ ends are still not defined.

The flowchart for the above PCR process is as below: