Developmental Validation of a DIP-InDel/DIP-STR System for the Detection of Unbalanced DNA Mixtures

Area of Science:

• Forensic Genetics
• Molecular Biology
• Human Identification

Background:

• Detecting minor DNA contributors in unbalanced mixtures is vital for forensic investigations.
• Allele-specific amplification of compound markers has emerged as a key technique for mixed stain analysis.

Purpose of the Study:

• To develop and validate a multiplex system for identifying minor DNA donors in unbalanced mixtures.
• To assess the utility of DIP-linked length polymorphic markers for forensic applications and noninvasive prenatal diagnosis.

Main Methods:

• Selected 18 DIP-InDel markers and combined them with 6 DIP-STR markers in a multiplex system.
• Estimated allele frequencies in 200 samples from the Chinese Han population.
• Evaluated the sensitivity, specificity, and minor contributor detection limit of the multiplex system.

Main Results:

• 23 of 24 DIP-linked markers showed high informativeness (I value >0.267) in the Chinese Han population.
• The multiplex system demonstrated high sensitivity (detecting >0.025 ng) and specificity for human DNA.
• Successfully detected minor contributors at 1% in unbalanced mixtures and identified paternal alleles in maternal plasma samples (27–40 weeks gestation).

Conclusions:

• DIP-linked length polymorphic markers provide a convenient method for detecting minor donors in unbalanced DNA mixtures.
• The developed multiplex system shows significant promise for forensic identification and noninvasive prenatal diagnosis.