Final answer:
To determine if a DNA sample contains GM DNA sequences, PCR uses specific primers that bind to the said sequences. These primers, combined with Taq polymerase and other reagents, facilitate the amplification of the GM DNA if present, allowing for its subsequent detection.
Step-by-step explanation:
In a Polymerase Chain Reaction (PCR) to determine whether a DNA sample contains genetically modified (GM) DNA sequences, specific primers are utilized. These primers are short sequences of DNA designed to be complementary to the ends of the specific GM sequence of interest. When combined with the sample DNA, Taq polymerase, and deoxynucleotides, the primers initiate the amplification of the target DNA if it is present. PCR is extremely sensitive and can amplify a DNA fragment from very small amounts of starting material, making it possible to detect the presence or absence of GM DNA with high precision. Taq polymerase is a crucial enzyme in PCR, derived from the heat-resistant bacterium Thermus aquaticus, which allows for the high temperatures necessary for PCR cycling without the enzyme denaturing.
The process involves multiple cycles of heating and cooling, which denature the DNA, allow primer binding, and permit new strand synthesis by Taq polymerase. If the GM DNA sequence is present in the sample, it will be exponentially amplified, allowing for easy detection through subsequent analysis such as gel electrophoresis. Conversely, if the GM sequence is not present, no significant amplification will occur.