Q.A cell free method of amplifying DNA first developed in the mid 1980's revolutionized the field of biotechnology. Name the method and explain the basic steps of the technique involved.

The method described is the Polymerase Chain Reaction (PCR).

PCR is a cell-free technique that amplifies a specific DNA segment exponentially through a series of repeated cycles. The basic steps involved in each cycle are:

• Denaturation: The double-stranded DNA is heated to a high temperature (typically 94-96°C) to break the hydrogen bonds between the complementary strands, separating them into single strands.
• Annealing: The temperature is then lowered (typically 50-65°C) to allow two sets of synthetic oligonucleotide primers to bind to specific complementary regions on each of the separated single-stranded DNA templates. …

The mid-1980s marked a pivotal moment in biotechnology with the development of a revolutionary cell-free method for amplifying DNA. Before this, obtaining sufficient quantities of a specific DNA segment for study or manipulation often required cloning it into a host organism, a process that was time-consuming and laborious. The new technique offered a rapid, efficient, and in vitro alternative, fundamentally changing how genetic material could be analyzed and utilized.

The method that transformed the field is called Polymerase Chain Reaction (PCR). It was developed by Kary Mullis in 1983 and quickly became an indispensable tool in molecular biology, diagnostics, and forensic science. PCR allows for the synthesis of millions to billions of copies of a specific DNA sequence from even a minute amount of starting material, all within a test tube.

The basic steps of the PCR technique involve a series of temperature-dependent reactions that are repeated multiple times, typically 20-35 cycles, in an automated instrument called a thermal cycler. Each cycle consists of three main steps:

• Denaturation: The reaction mixture, containing the target DNA, is heated to a high temperature, typically 94-96°C. This high heat breaks the hydrogen bonds between the complementary base pairs of the double-stranded DNA template, causing the two strands to separate. This creates single-stranded DNA templates that can be copied.

• Annealing: Following denaturation, the temperature is lowered to an optimal range, usually 50-65°C. At this temperature, short, synthetic single-stranded DNA molecules called primers bind to their complementary sequences on the separated single-stranded DNA templates. Two primers are used for each target DNA segment, one for each strand, flanking the region to be amplified. The primers serve as starting points for DNA synthesis.

  Note

  Primers are crucial because DNA polymerase, the enzyme responsible for synthesizing new DNA, cannot start a new strand from scratch; it can only add nucleotides to an existing 3′-hydroxyl group. …