Which components provide the building blocks for DNA synthesis in PCR?

• A. Enzymes
• B. Primers
• C. Nucleotides
• D. Buffers

Answer: (C)

DNA synthesis in PCR relies on the four nucleotides that become the new DNA strands: the building blocks dATP, dTTP, dCTP, and dGTP. DNA polymerase uses these substrates to extend the growing DNA chain by adding one nucleotide at a time in a sequence complementary to the template strand (A pairs with T, G pairs with C). Primers provide the starting point for synthesis, but they are not the materials that form the new DNA themselves. Buffers keep the reaction conditions stable, and enzymes act as catalysts to speed up the process, yet they do not supply the actual building blocks. Therefore, the nucleotides are the components that directly supply the material for DNA synthesis in PCR.