What is PCR used to amplify?

PCR, or polymerase chain reaction, is a powerful molecular biology technique primarily used to amplify specific segments of DNA. The fundamental principle behind PCR involves creating millions of copies of a targeted DNA sequence, enabling researchers to analyze minute amounts of DNA in a sample.

This amplification is achieved through a series of temperature cycles that enable the denaturation of the DNA, annealing of primers that flank the target region, and extension of those primers by DNA polymerase, ultimately resulting in significant quantities of the desired DNA segment. This technique is critical in many applications, including genetic testing, forensic analysis, cloning, and research on genetic variation.

The other options refer to different processes or biological molecules, such as protein analysis, whole genome amplification, or the study of RNA, which involves techniques other than PCR. Thus, the use of PCR specifically relates to DNA amplification, confirming that the correct answer is indeed focused on specific segments of DNA.