What are internal size standards used for in PCR analysis?

Internal size standards in PCR analysis are critical for accurately determining the size of PCR products. These standards are essentially molecular weight markers that consist of DNA fragments of known lengths. When these standards are included in the analysis, they facilitate the estimation of the size of unknown PCR products by comparison.

In the context of PCR, knowing the size of the amplified fragments is vital for confirming the presence of specific target sequences, assessing the efficiency of the PCR reaction, and determining if the expected product has been generated. By running the PCR products alongside these predefined size markers on a gel, researchers can effectively visualize and quantify the size of their PCR amplifications, ensuring that they align with the expected results based on the target DNA.

The other options do not accurately reflect the primary role of internal size standards in PCR. For instance, identifying specific pathogens involves more specialized techniques like sequencing or real-time PCR with specific probes, while enhancing reaction temperatures is related to the PCR process parameters rather than size determination. Additionally, DNA purification involves removing contaminants from DNA samples, which is separate from the function of size standards.