It turns out that animals and plants can also do "paternity tests"

　　Identification of non-human DNA uncovers mystery of shark origins

　　□ Our reporter Yu Dongming

　　□ "Legal and News" reporter Huang Haodong

　　□ Our correspondent Ruan Junfeng

　　Looking at the 10 containers of shark fins, forensic doctor Zhang Suhua couldn't help frowning. After all, finding the fins of "endangered wild sharks" from so many shark fins is like looking for a needle in a haystack.

　　In January this year, the Coast Guard commissioned the Academy of Forensic Identification Sciences (hereinafter referred to as the “Jianjian Institute”) to conduct species identification for a batch of smuggled shark fins seized not long ago, to determine whether the batch of shark fins contained shark fins from endangered wild sharks, so that the Better fight crime.

　　The reporter learned that the Forensic Evidence Research Office of the Si Jianyuan has already deployed non-human DNA identification five years ago, and has successively completed the scientific research, technical research, equipment configuration of related projects, until the establishment of a non-human DNA identification laboratory. .

Beginning in 2020, "non-human DNA identification" has been listed as a routine business scope for forensic evidence identification for the first time.

　　"Non-human DNA identification includes identity identification, species identification and kinship identification for samples other than humans such as animals, plants, microorganisms, etc., which is somewhat similar to 'paternity testing' for animals and plants." Zhang Suhua is an industry leader A young top-notch talent, her team is also a leading team in scientific and technological innovation, with strong research strength and outstanding technical ability.

According to the arrangement of the research team, she is mainly responsible for the technical research and specific identification business of non-human DNA identification.

Through several years of exploration, she has accumulated a wealth of work experience.

　　However, when Zhang Suhua and her colleagues arrived at the site where the smuggled shark fins were stored and seized, they saw that snakeskin bags filled with shark fins were scattered in 10 large containers. Deterioration, some serious corruption even have maggots crawling, each container exudes a strong stench, even wearing masks and protective clothing, everyone is still smoked lightly, and the smell on the body will not be released for a few days. go out.

　　Shark fin is a precious ingredient that has been sought after by people since ancient times. However, making shark fin requires cutting the fin from a live shark. A shark that loses its fin is almost equivalent to being sentenced to death.

Looking at the 10 containers of shark fins in front of him, Zhang Suhua, who has always loved nature and animals, made up his mind to find out the "life experience" of these shark fins and crack down on those criminals in accordance with the law.

　　"It is impossible for such a large number of shark fins to be completely identified. Our team decided to conduct sampling and identification after deliberation." Zhang Suhua said that with the help of the coast police officers, she and her colleagues moved the shark fins out of the container together. This process alone lasted nearly two hours.

　　It was January and the weather was gloomy and cold, but Zhang Suhua and his colleagues were still sweating from exhaustion.

　　After weighing and statistics, the seized shark fins weighed about 4 tons and were packed in 137 snakeskin bags.

Zhang Suhua and his colleagues decided to take two samples from each bag of shark fins, and then sent them back to the Si Jianyuan for identification.

　　It was difficult to complete the statistics of the number of shark fins, but there was another trouble in sampling.

"The biological cell content of shark fins is very rare, and most of them have deteriorated and corrupted, so sampling must be more careful, otherwise the secondary damage will lead to the failure to extract effective DNA normally." Zhang Suhua said, "The cell content in shark fin cartilage is similar to that of shark fin cartilage. It is more concentrated than other parts, and it is also the part where DNA information is the easiest to extract. After careful inspection, we decided to sample from this part."

　　Extracting shark fin cartilage is a very delicate job. Zhang Suhua and the others have to strictly disinfect and clean all shark fins before foaming them before sampling.

The cartilage of shark fins is very slender. In order not to damage the samples, they can only work slowly and carefully. It took them almost a whole day to complete the sampling of all the shark fin samples.

　　Once available samples are available, formal species identification is the next step.

　　"The identification of biological species usually starts with the identification of appearance or DNA, but the sample submitted this time is only a small part of the shark fin, which is difficult to distinguish from the shape. We can only obtain relatively accurate results through DNA comparison. ." Zhang Suhua said, they chose to PCR-amplify two mitochondrial genes in shark fin tissue.

　　PCR amplification is a molecular biology technology used to amplify specific DNA fragments. Identification of shark fins.

Through this technology, Zhang Suhua and the others successfully extracted gene sequences for comparison from 135 samples.

　　After extracting the gene sequence, the next step is to perform sequence alignment.

"Sequence alignment is based on the sequence structure in biology. If both nucleic acid sequences and sequences on the primary structure of proteins are regarded as strings, the similarity between sequences can be detected through the alignment between strings. "Speaking of his profession, Zhang Suhua is right.

　　They used software to compare the extracted sample gene sequence with the shark gene sequence recorded in the internationally recognized National Center for Biotechnology Information database. match the shark gene sequence.

　　The bigeye thresher, also known as the deep-sea thresher, is distributed in tropical waters off the coast of Taiwan, China. The IUCN listed this shark as a vulnerable animal in 2018, and it is also a member of the Convention on International Trade in Endangered Species of Wild Fauna and Flora. "species listed in the appendix.

　　In order to enhance the scientific rigor of the sequence alignment results, Zhang Suhua et al. also provided support for the identification through "phylogenetic tree" analysis.

　　"'Phylogenetic tree' is a method of describing the correlation between different organisms in bioinformatics. By constructing a phylogenetic tree, the source of a certain gene sequence can be traced." Zhang Suhua found through experiments that the gene sequence of the sample is closely related to the large The genes of the thresher sharks belonged to homology, which further verified the results of the software comparison.

　　Through comparison, Zhang Suhua and her colleagues finally determined that 97 of the 135 samples identified belonged to the bigeye thresher.

After conversion, the Ministry of Justice issued a report on the identification results, and found that about 71.8% of the total 4 tons of shark fins seized by the Coast Guard belonged to this species.

At present, the Shanghai police have filed an investigation on suspicion of smuggling endangered species.

　　Since non-human DNA identification has been included in the scope of forensic material evidence identification, Zhang Suhua has successively participated in forensic identification cases such as Chinese sturgeon species identification, racing pigeon individual identification and kinship identification, pig and cattle paternity identification and other forensic identification cases. have a deep understanding.

　　Identification material from plants and animals is very different from human tissue, and these differences often make identification more difficult.

Zhang Suhua recalled a case in which she participated in the identification of wood species. At that time, she wanted to identify a wooden furniture chair and confirmed the source of the wood for the manufacture of the chair.

Because the wood has been deeply processed, it is quite difficult to extract plant DNA, and the entire identification process takes a lot of time and effort.

　　In addition, non-human DNA identification is a brand-new identification project, and the lack of industry standards and authoritative data is also a major difficulty in identification work.

Zhang Suhua said frankly that at present, the comparison of non-human DNA largely relies on the information recorded in foreign public databases.

　　In this regard, the Ministry of Justice has also taken active measures to deal with it.

This year, the Court of Justice has completed the formulation of industry standards for cannabis plant species and individual identification, which are currently being promulgated. Forensic identification of plants provides identification reference.

In addition, the Si Jian Institute has built its own DNA barcode database including hallucinogenic plants and poisonous mushrooms, which provides a basis for the comparison of gene sequences of these species.

　　"At present, we are still in the process of establishing a non-human DNA database for forensic medicine to fill the data gap of domestic non-human forensic identification." Zhang Suhua said that scientific exploration has no end. Unravel more unsolved mysteries for mankind.