Statement I: ELISA operates on the basis of antigen-antibody interaction.

Statement II: It aids in the early detection of diseases or pathogens by targeting and detecting specific antigens or antibodies, through the amplification of their nucleic acid.

Only statement I is correct .

Statement I is correct. ELISA is a laboratory technique that uses the specific binding of antibodies to antigens to detect the presence of a target molecule in a sample. The antigen-antibody interaction is highly specific, making ELISA a very sensitive and accurate method for detecting the presence of diseases or pathogens.

Statement II is incorrect. ELISA does not amplify the nucleic acid of the target molecule. Instead, it relies on the specific binding of antibodies to the target molecule to produce a signal that can be detected. The signal can be produced by a variety of methods, including the use of enzymes, fluorophores, or chemiluminescent molecules. It is commonly used in medical diagnostics and research to identify the presence of diseases, pathogens, or specific proteins in patient samples, body fluids, or experimental samples.

To clarify, the amplification of nucleic acids is typically associated with techniques like Polymerase Chain Reaction (PCR) and other nucleic acid amplification methods used for the detection of specific DNA or RNA sequences, not with ELISA.

So the correct answer is Statement I only.