What type of sequence can PCR detect?

Polymerase Chain Reaction (PCR) is a widely used technique in molecular biology that is specifically designed to amplify DNA sequences. The PCR process involves several key steps: denaturation, annealing, and extension, which are vital for duplicating the target DNA in the sample. During denaturation, the double-stranded DNA is heated to separate its strands, while in the annealing step, short DNA primers bind to complementary regions of the target DNA. Finally, DNA polymerase extends these primers to create new strands of DNA, effectively amplifying the original sequence.

While PCR can be adapted to work with cDNA (complementary DNA synthesized from RNA), the primary target of PCR is DNA sequences. In contrast, the other options—RNA sequences, protein sequences, and amino acid sequences—cannot be amplified directly by PCR as they either involve RNA (which would require reverse transcription to convert to DNA) or are not nucleic acids at all, but rather the end products of gene expression (proteins composed of amino acids). Therefore, the ability of PCR to specifically detect and amplify DNA sequences makes it a crucial tool in various applications, including genetic research, diagnostics, and forensics.