The process of paternity testing in West China Hospital:
The steps of DNA paternity testing are as follows:
Step 1: DNA extraction
The DNA contained in the nucleus of the sample cells is extracted, and then purified to remove impurities in the sample.
Second step: PCR amplification
PCR is the Chinese name for Polymerase Chain Reaction. Simply put, PCR amplification is the step where the fragments we need are enzymatically replicated on a PCR machine and amplified to the extent that they can be seen by certain specialized instruments.
Step 3: Post-PCR reaction
This step is mainly the preparation stage for the ABI sequencer, which opens up the double-stranded DNA and adds some internal markers for the test, mainly used to mark the length of the fragments to be tested.
The fourth step: capillary sequencer detection
Since DNA has an electric charge, through the method of capillary electrophoresis, the electrophoretic speed of different fragments of DNA length is different, and the distance of swimming is different under the same voltage and the same electrophoresis time, these different distances can be distinguished through the measurement of the internal standard added in the early stage, and at the same time, it can be displayed in the computer through certain software, which is convenient for the testing personnel to process and analyze the data. It is convenient for inspectors to handle and analyze the data.
The fifth step: analyze the data, issue a report
The main test personnel will be the results of the analysis of the summary, calculations, and then out of the identification of conclusions and reports.
Expanded Information:
DNA Identification
The most commonly used method of paternity identification is DNA typing. Human blood, hair, saliva, oral cells and bones can all be used for paternity testing, which is very convenient.
A person has 23 pairs (46) of chromosomes. A pair of genes at the same location on the same pair of chromosomes is called an allele, usually one from the father and one from the mother. If an allele is detected at a particular DNA locus, and one is the same as the mother, the other should be the same as the father, otherwise there is doubt.
The use of DNA for paternity testing, as long as a dozen to dozens of DNA loci for the test, if all the same, you can determine paternity, if there are more than three loci are different, can be ruled out paternity, there are one or two loci are different, then we should consider the possibility of genetic mutation, plus do some loci of the test for identification. DNA paternity testing, the accuracy of the paternity denial The accuracy of DNA paternity testing is nearly 100%, and the accuracy of certainty of paternity can reach 99.99%.
DNA paternity testing is mainly determined by the following characteristics
Somatic cell stability: the DNA of the same body's blood, saliva, semen, and various organs and tissues is consistent, and is unchanged throughout the life of the same healthy person, which is the most basic premise.
Individual High Specificity: Differences in genetic nature at the molecular level of DNA in different individuals dictate that the same restriction enzyme digests genomic DNA , and it is impossible for the allelic fragments of one individual to be the same as those of another in number and length, thus producing DNA that is individual-specific.
Inherited according to Mendelian laws of inheritance: it has been proved through a large number of family line investigations that all allele bands in the DNA of the offspring can be found in the DNA of both parents, and that the transmission of the fragments is in accordance with Mendelian laws of inheritance.
Baidu Encyclopedia - Paternity Testing