How to do DNA paternity test?

In most cases, there is no need to do a DNA paternity test during pregnancy, but some special circumstances are inevitable. Today's society is more complicated. Some women do not know who the father of the fetus is after they become pregnant. At this time, the easiest way is to do a sperm paternity test, which is also the most convenient and accurate identification method. So how is the DNA paternity test done specifically?

How to do DNA paternity test?

DNA fingerprint

DNA fingerprint refers to DNA polymorphism that is completely individual-specific. Its individual identification ability is comparable to that of finger fingerprints, hence the name. It can be used for personal identification and paternity testing. By hybridizing with enzyme-cut fragments of human nuclear DNA, a hybridization band pattern of varying lengths composed of alleles at multiple sites is obtained. This pattern is rarely exactly the same in two people, so it is called a "DNA fingerprint."

Because DNA fingerprints have high variability and stable heritability, and are still inherited in a simple Mendelian manner, they have become the most attractive genetic marker and can be widely used in paternity testing.

Features: 1. High specificity: Studies have shown that the probability that two random individuals have the same DNA pattern is only 3×10^-11; if two probes are used for comparison at the same time, the probability that two individuals are exactly the same is less than 5×10^-19. The world population is about 5 billion, or 5×10^9. Therefore, unless they are identical twins, it is almost impossible for two people to have exactly the same DNA fingerprint pattern. 2. Stable inheritance: DNA is a person's genetic material, and its characteristics are inherited from parents. The analysis found that almost every band in the DNA fingerprint map can be found in the map of one of its parents. This band conforms to the classic Mendel's law of inheritance, that is, the characteristics of both parties are passed on to the offspring at an average of 50%. 3. Somatic cell stability: that is, the DNA fingerprint patterns produced by different tissues of the same person, such as blood, muscle, hair, semen, etc., are completely consistent.

STR Testing

Short tandem repeat (STR), also known as microsatellite DNA, is a type of DNA polymorphic locus that is widely present in the human genome. It consists of a core sequence of 2 to 6 base pairs, arranged in tandem repeats. The length of STR gene loci is generally between 100 and 300 bp. It is highly polymorphic due to differences in DNA fragment length or DNA sequence between individuals and is inherited in a Mendel's codominant manner during gene transmission. Because of its short gene fragment, high amplification efficiency and accurate typing, it is called the second-generation DNA fingerprint. In recent years, this method has been widely used in paternity testing.

SNP

SNP has become the third-generation genetic marker. Many phenotypic differences in the human body, susceptibility to drugs or diseases, etc. may be related to SNP.

RFLP analysis

Restriction map markers and observable phenotypes Recombination frequency is measurable, dividing the genetic map into two molecular markers: genotypic and phenotypic. Restriction markers have become a powerful tool for determining genetic inheritance at the molecular level because they are not affected by genomic changes that affect the phenotype.

RFLP and SNP are the basis of linkage maps and are of great significance for parentage identification. For many genetic diseases that cause human disease, our location on the genetic map is known, but our corresponding gene sequence or protein is still unknown. For example, cystic fibrosis conforms to Mendel's laws of inheritance, but before the gene is marked, the molecular nature of its mutant is unknown. In the comparison of DNA restriction maps between patients and normal people, it is often found that specific restriction sites appear or disappear in their genomes. If a restriction marker is linked to a phenotypic trait, the restriction site is located near the gene for the phenotypic trait. Identifying this marker has the following two meanings: it provides a procedure for diagnosing the disease; it provides a reference for the isolation of the gene.