Can a disease be detected before its symptoms appear? Explain the principle involved.

Explanation

When the symptoms of the disease are not yet visible the pathogen concentratin is very low so, the detection by conv entional diagnostic tests is very difficult.
However, detection of a disease before the apperance of symptoms is possible by the amplification of victim's nucleic acid by PCR.
The principle involved here is that a single DNA molecule can be copied endiessly in a test tube using priemres, DNA polymerase enzyme and free nucleotides. the desired DNA of the pathogen is amplified b y PCR from a litied amount of DNA template.