Medicolegal identification method of species

Abstract

The invention discloses a medicolegal identification method of species and belongs to the technical field of medicolegal identification. The medicolegal identification method is characterized in that a biological sample mtDNA as a template and a 12SF1 / 12SR, 12SF2 / 12SR, COX1F / COX1R and 16SF / 16SR primer pair mixture as primers are subjected to PCR amplification; and PCR products are subjected to agarose gel electrophoresis, wherein when three electrophoretic bands are produced, the detected biological sample is human tissue, and when two electrophoretic bands are produced, the detected biological sample is animal tissue. The medicolegal identification method has the advantages that the seven primers of 12SrRNA, 16SrRNA and COX1 are subjected to multiplex amplification and the primers are subjected to specificity validation so that human and common animals comprising rhesus monkey can be distinguished; through three-primer multiplex amplification and two internal references, a result is more credible; and the medicolegal identification method has pg grade of sensitivity.

Description

technical field [0001] The invention belongs to the technical field of forensic identification, and in particular relates to a method for identifying species in forensic medicine. Background technique [0002] Species identification is an important step in forensic physical evidence examination, and the species identification of various biological samples extracted on site is the first and key link in other identifications. Its main task is to identify the source of the species of the scientific biological samples and determine whether the samples come from the human body. We used the method of PCR compound amplification and agarose electrophoresis detection to identify the species. [0003] Traditional species testing methods include nuclear DNA sequence specificity testing (PCR-RFLP), mtDNA sequencing analysis, and immunological testing methods, etc. At present, immunological test strip analysis is widely used in forensic examination. The principle is immunodiffusion exp...

AI Technical Summary

Problems solved by technology

[0005] 1. Alu sequence species identification method: Alu sequence is unique to humans and primates, and cannot be distinguished from humans and monkeys; Alu sequence is nuclear genomic DNA, and nuclear genomic templates are required for effective identification, which requires more DNA , so it reduces its sensitivity; and the content of mtDNA in animal cells is thousands of copies more than that of nuclear DNA, if there is a suitable method, the detection sensitivity will be greatly improved

[0006] 2. The mtDNA species inspection often adopts the method of sequencing, which is expensive. This method is to amplify and sequence some mtDNA coding genes, and compare their sequences in the gene bank for homology comparison before making a species judgment

Although this method may identify what kind of animal the sample comes from, the detection process is cumbersome and the sequencing cost is expensive; and it is more common in forensic practice to determine whether the biological sample comes from humans

[0007] 3. Species inspection test strips commonly used by public security: First, the species test strips currently used in public security inspections are test strips for blood and semen spots, which can only detect the species specificity of blood or semen spots. For other Tissues such as bone, hair, and saliva are powerless; secondly, the specificity of the test strip test is not high, and monkeys may be mistakenly detected as human; finally, it is very important that biological samples at the scene of criminal cases will be affected by many factors, such as Influenced by rain, enzymatic hydrolysis, pollution, etc., while protein molecules are easily denatured and degraded and affected by the environment, immune test strips are prone to false negative results

In this way, if the species inspection is carried out first according to the conventional method, the remaining inspection materials are not enough for STR typing, or even the inspection materials are not enough for species inspection at all, resulting in waste of inspection materials and evidence

However, direct STR typing may cause false exclusions. The reason is that when encountering forensic trace samples (pg-level samples, such as blood-stained samples smaller than the size of rice grains, etc.), because the amount of samples is too low, in order to If you get STR typing, you may give up the species test (the amount of material required for species test is much larger than that required for DNA-STR typing) and directly perform DNA-STR typing test, if you get a complete typing result. Determine or exclude suspects, but when only partial STR typing results are obtained (due to sample degradation, trace or contamination, amplification system, etc.), since not all STR loci are species-specific, such Part of the STR typing obtained may be caused by animal tissues, or it may be human tissue, but not all STR typing is obtained. If suspects are identified or excluded based on this, erroneous conclusions are often drawn, especially false negatives (false exclusion)

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