Molecular diagnosis refers to the application of molecular biology methods to detect changes in the structure or expression level of genetic material in patients to make a diagnosis. Molecular diagnosis is the main method for predictive diagnosis, which can be used for the diagnosis of individual genetic diseases and prenatal diagnosis. Molecular diagnosis mainly refers to the detection of genes encoding various structural proteins, enzymes, antigen antibodies, and immune active molecules related to diseases.

The main technologies of molecular diagnosis are nucleic acid molecular hybridization, polymerase chain reaction and biochip technology.

1. Nucleic acid molecule hybridization technology has a process in which a certain complementary sequence and a nucleotide single strand associate into a heteroduplex in liquid or solid phase according to the principle of base complementary pairing, which is called nucleic acid molecule hybridization. The two sides of hybridization are the nucleic acid sequence to be detected and the probe sequence. The application of this technology allows qualitative or quantitative detection of specific DNA or RNA sequences.

2. Principle of polymerase chain reaction (ie Polymerase chain reaction, PCR): PCR is template DNA, primers and four deoxyribose ribose triphosphates (dNTPs) undergo enzymatic polymerization under the action of DNA polymerase, and amplify all Target DNA is required. It consists of three basic steps: heat denaturation of double-stranded DNA template to single-stranded (denaturation); complementary pairing of primers and single-stranded DNA at low temperature (annealing); TapDNA polymerase catalyzes the extension of primers along the template DNA at a suitable temperature.

3. Biochip technology is a nucleic acid analysis and detection technology that combines molecular biology and microelectronics technology developed in recent years. The main goal of the initial biochip technology is for DNA sequence determination, gene expression profile identification and gene mutant detection and analysis, so it is also called DNA chip or gene chip technology. Since this technology has been extended to non-nucleic acid fields such as immune response and receptor binding, protein chips, immune chips, cell chips, tissue chips, etc. have appeared, so the renaming of biochip technology is more in line with the development trend.