Editing Content :: Admin Scraper

Chapter

Content type

Position

Value

structure of the proteins. They are transferred to a nitrocellulose membrane. The desired protein is detected on membranes using an antibody specific to the protein (Fig. 3.17). Using all the three blotting techniques, a person can identify a gene and its expression. For example, a gene in a DNA sequence can be identified by Southern blotting, and its transcripts (RNA) can be identified by northern blotting, and finally the expression of a protein from mRNA (by translation) by western blotting. Box 3: Eastern Blot Eastern blot is used for the detection of specific post-translational modification of proteins. Proteins are separated by gel electrophoresis before being transferred to a blotting matrix where upon post-translational modifications are detected by specific substrates (cholera toxin, concanavalin, phosphomolybdate, etc.) or antibodies 3.7 P olymerase C hain R eaction (PCR ) Several molecular and genetic experiments require significant amount of DNA. In order to generate multiple copies of DNA from a few copies, a technique was developed by Kary B. Mullis, which is known as ‘Polymerase Chain Reaction (PCR)’. In this technique, a very small amount of DNA can be exponentially amplified to generate thousands to millions of copies. PCR, sometimes called ‘molecular photocopying’, is often heralded as one of the most important scientific advances in molecular biology that revolutionised the study of DNA to such an extent that its inventor, Kary B. Mullis was awarded the Nobel Prize for Chemistry in 1993. PCR technique is based on the principle that cells use to replicate its DNA. As the name implies, it is a chain reaction carried out in repeated cycles, which involves the process of heating and cooling called thermal cycling carried out by a machine called thermocycler. It requires a heat stable DNA polymerase enzyme that can make new strands of DNA on template strands at a high temperature of about 72 to 78°C (a temperature at which a human or E. coli DNA polymerase would be non-functional). DNA polymerase typically used in PCR is called Taq polymerase, an enzyme isolated from the 52 BiotechnologyXII Reprint 2025-26