Question

Distinguish between PCR and gene cloning. Explain the importance of gene cloning.

Answer 1

ene cloning is a technique employed to locate and multiply a specific gene from the extracted genomic DNA of an organism through the construction of recombinant DNA. Genomic DNA contains thousands of different genes encoded for proteins. When DNA is extracted, it includes all possible genes it can bear. Gene cloning technique has enabled the detection of a specific gene from the total DNA. Therefore gene cloning serves as an important tool in molecular biology.

Making of a genomic library of an organism is essential in gene cloning if there is no clue about the location of the relevant gene in the DNA. A genomic library is made using the following steps.

Step 1: Extraction of the total DNA from an organism which contains the desired gene.

Step 2: Restriction digestion of the extracted DNA to produce small manageable fragments. This step is facilitated by restriction endonucleases.

Step 3: Selection of a suitable vector and opening the vector DNA using the same restriction endonucleases. Bacterial plasmids are commonly used as vectors to carry foreign DNA. Plasmids are small circles of DNA located within bacteria.

Step 4: Combining of the vector DNA and fragmented DNA to produce recombinant DNA molecule. This step is governed by DNA ligase.

Step 5: Transferring of recombinant DNA molecules into host bacteria. This step is known as transformation, and is done using a heat shock.