The principle of paternity test

The basic principle of paternity test: The human genome is a system with very stable structure, and at the same time it is a system with variation. In the process of long-term evolution, the sequence of genomic DNA is constantly changing. Some of these mutations are preserved, which leads to differences and polymorphisms in genomes among different races, groups and individuals. No two individuals have the same genome except identical twins.

Paternity identification is based on the theory and practice of human genetics, analyzing the genetic characteristics from the morphological structure or physiological function of offspring and parents, judging the suspicious biological relationship between father and son or mother and child, and making positive or negative conclusions. The methods of paternity test in forensic medicine include blood group identification, appearance comparison, skin texture examination, genetic disease examination, earwax difference, taste blindness examination, pregnancy, childbirth and reproductive ability inference.

Principles and procedures of DNA paternity

DNA is extracted from a few drops of blood, cheek cells or cultured tissue fibers. Cut the DNA sample into small pieces with domain elements, put it into the gel, and push the DNA pieces with an electrophoresis tank to separate them-the thinnest is farthest and the largest is nearest. After that, the isolated genes are placed on nylon membrane, and special DNA probes are used to find genes, and the same genes will be condensed into one. Then, with special dyes, in the X-ray environment,

Displays a black barcode condensed by a DNA probe. The barcode visible to the naked eye of the child is very special, half of which matches the mother's and half matches the father's. This process is repeated several times. Each probe is used to find different parts of DNA and map them into a unique barcode. With several groups of different probes, more than 99.9% paternal probability or resolution can be obtained.