“Molecular” is the study of nucleic acids and protein.
Molecular diagnostics is the application of molecular biology to medical testing.

Molecular diagnostics is the laboratory examination of DNA, RNA, and protein.

Molecular technologies include electrophoresis, the polymerase chain reaction (PCR), blotting and hybridization assays, sequencing, and microarrays.
These techniques are used to diagnose and monitor disease, detect risk, and decide which therapies will work best for individual patients (pharmacogenomics).
Molecular techniques can also be used to match donors and recipients for organ transplantation, identify missing or disaster victims, determine parentage, detect and quantify infectious disease agents, and, of course – forensics.