PCR procedures

PCR is a fast and inexpensive technique used to “amplify“, or copy, small segments of DNA. Because significant amounts of a sample of DNA are necessary for molecular and genetic analyses, studies of isolated pieces of DNA are nearly impossible without PCR amplification.

PCR is valuable in a number of laboratory and clinical techniques, including DNA fingerprinting, detection of bacteria or viruses, and diagnosis of genetic disorders. To amplify a segment of DNA using PCR, the sample is first heated to 94-98 Celsius degrees so the DNA denatures, or separates into two pieces of single-stranded DNA. Next, an enzyme called “Taq polymerase” synthesizes, or builds, two new strands of DNA, using the original strands as templates.

Professor Lee demonstrates an example of a positive signal from a shrimp intestinal sample. The DNA ladder, represented by “M,” or commonly referred to as the DNA marker, is present. Samples 1 and 2 are the PCR products amplified from genomic DNA extracted from a diseased shrimp intestine, providing evidence that the shrimp suffered from early mortality syndrome due to V. parahaemolyticus infection.

Next week, we will discuss how to extract RNA, synthesize complementary DNA, and what factors to consider before conducting PCR.

Review questions: – What is PCR, and why is it valuable in molecular and genetic analyses? – How can PCR be used in the diagnosis of genetic disorders or the detection of bacteria or viruses?