Development of a new 25plex STRs typing system for forensic application.

Area of Science:

• Forensic Genetics
• Molecular Biology
• Population Genetics

Background:

• Short tandem repeat (STR) analysis is crucial for forensic identification and paternity testing.
• Existing multiplex STR kits may not cover sufficient loci or include novel markers for enhanced discrimination.
• The need for highly polymorphic and informative STR markers for diverse populations is critical.

Purpose of the Study:

• To develop and validate a novel 25-plex fluorescence multiplex STR kit (DNATyper25) for forensic and paternity applications.
• To genotype 23 autosomal and 2 sex-linked loci, including 20 non-CODIS autosomal STRs.
• To assess the kit's performance in terms of reproducibility, accuracy, sensitivity, specificity, and robustness.

Main Methods:

• Development of the DNATyper25 multiplex STR kit.
• Conducting developmental validation studies including sensitivity, specificity, and stability tests.
• Genotyping 509 individuals from the Chinese Han population to evaluate forensic efficiency parameters and population genetics.

Main Results:

• The DNATyper25 kit demonstrated high sensitivity, achieving full profiles with 125 pg of DNA.
• Specificity testing confirmed no cross-reactivity with common non-human DNA contaminants.
• Forensic evaluation in the Chinese Han population showed high polymorphism and informativeness, with a high probability of exclusion (TDP) and combined power of discrimination (PM).

Conclusions:

• The DNATyper25 kit is a reproducible, accurate, sensitive, and robust tool for forensic and paternity analysis.
• The novel autosomal STR loci are highly informative in the Chinese Han population, aiding in difficult paternity cases and low-quality DNA samples.
• The kit's performance supports its utility in forensic casework and population genetic studies.