A mixture detection method based on separate amplification using primer specific alleles of INDELs-a study based on...

Area of Science:

• Forensic Science
• Genetics
• Molecular Biology

Background:

• Unbalanced DNA mixtures pose challenges in forensic and clinical DNA analysis.
• Traditional Short Tandem Repeat (STR) and Single Nucleotide Polymorphism (SNP) typing methods suffer from PCR amplification bias, masking minor DNA contributors.
• A sensitive and accurate method is needed to detect low-level DNA in mixtures.

Purpose of the Study:

• To develop and validate an allele-specific Insertion/Deletion (INDEL) genotyping method for detecting unbalanced DNA mixtures.
• To assess the sensitivity and reliability of this new method compared to traditional techniques.
• To establish a practical approach for forensic DNA examination.

Main Methods:

• Fourteen INDEL markers were analyzed in the Chinese Han population.
• Real-time PCR with two separate primer-specific reactions was employed for INDEL amplification.
• The difference in Ct values (D-value) between the two reactions was used to determine DNA source and detect mixtures.
• Electrophoresis was used for further confirmation of INDEL types.

Main Results:

• The INDEL genotyping method demonstrated high sensitivity, detecting minor DNA contributors at ratios as low as 1:50 to 1:1000, significantly outperforming traditional STR typing.
• The D-value analysis effectively distinguished single-source DNA from mixtures, with specific D-value ranges indicating the presence of a mixture.
• The detection limit for real-time PCR was between 0.3125 ng and 1.25 ng of template DNA across all 14 INDEL markers.

Conclusions:

• The proposed allele-specific INDEL genotyping method is a sensitive and convenient approach for detecting unbalanced DNA mixtures in forensic samples.
• This real-time PCR-based strategy offers a promising alternative to conventional methods, particularly for analyzing complex DNA samples.
• The method is validated for the Chinese Han population and has significant implications for forensic DNA analysis.