A Centuries-old problem calls for more scientific solutions

Seasoned Chinese TV viewers who are fascinated with historical detective soap operas often watch with trepidation whether Di Xue Ren Qin, an ancient technique employed by Chinese judges to identify criminals and by ordinary people to find relatives who had long gone astray, could lead to grave errors. In the former case, innocent people could be unjustly penalized, while in the latter case, people with no kinship could be artificially brought together as relatives.

The technique, which was first adopted as early as the Song Dynasty and was widely regarded as beyond doubt at the time, involves the combination of a drop of blood from the known person and another drop of blood from the suspected person. If the two blood drops could mix up, the target person and the person in suspect will be considered as having kinship between them. Otherwise, they are not regarded as related. But, the then widely used technique does not seem to have a sound scientific basis, thus becoming a potential source of error of its own with dire consequences.

Now, thanks to the advancement of modern molecular biology, promising new techniques have emerged to resolve this centuries-old problem. All these techniques have a solid genetic basis, with DNA at the core of the solution. One such technique is called fragment analysis.

What is Fragment Analysis?

As a molecular biological technique, fragment analysis is a method for analyzing DNA fragments of various nucleotides of different sizes produced in the PCR process. It can measure the size of DNA fragments by comparing them with DNA fragments whose size is already known.

At the core of fragment analysis is the separation of multiple PCR technology from the capillary electrophoresis system. Multiple primers are included into the same PCR reaction system, and the primers specifically combine the corresponding target genes for PCR multiplexing. The capillary electrophoresis system can be used to separate and identify PCR products with different fragment lengths. Quantitative analysis of different products can also be carried out.

A typical fragment analysis process consists of the following steps:

Extract nucleic acids (i.e. RNA and DNA) from biological samples such as sputum, tissues and blood, prepare templates and primers, perform multiple PCR, then adopt any of capillary electrophoresis, PAGE electrophoresis, DHPLC, HPLC and Gel electrophoresis for fragment analysis, and finally conduct data analysis.

Fragment analysis has found various applications in a wide range of fields. Genotyping, DNA fingerprinting and parentage identification are some common applications of fragment analysis.

How Fragment Analysis Can Help Parentage Identification?

Sequencing of human genomes sheds great light on genetic variations between individuals. It is then only too natural to examine such allelic variations, which is extremely useful for identity recognition in both forensic and paternity tests. Distinctive features are often associated with different identities or groups. Moreover, fragment analysis can help to specifically trace genetic disorders to some peculiar chromosomes, thus establishing possible links between genetic variations to the diseases of a particular community, family or population.

With its multiplexing of fluorescently labeled products in both size and color, fragment analysis affords accurate identification of kinship linkages between individuals. In other words, fragment analysis can be a powerful tool for parentage identification. Automated sequencing has greatly aided this process.

Future Prospect
Bartley et al has called fragment analysis a changing field which holds great promises. Indeed, advanced fragment analysis has already made great headways in both technological innovation and practical applications. In the future, we may see the unraveling of ancient mysteries in the light of modern science. Let’s hold our breath for more excitement!

Author's Bio: 

This article is written by scientists from BOC Sciences. As an industry-leading chemical supplier, BOC Sciences not only provides professional services such as Antibody drug Conjugates and Fluorescent labeling to facilitate various research efforts, but also focuses more on the drug discovery by providing techniques like screening libraries , DNA Encoded Library , Virtual Screening , etc.