DNA Methylation Analysis for Forensic Body Fluid Identification
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Solution Overview
Problem
Current forensic methods for identifying the source of body fluids, such as semen, blood, and vaginal secretions, are unreliable due to low sensitivity and the potential for false positives/negatives, and often require additional sample processing for RNA analysis after DNA isolation, which can consume the original sample.
Innovation Solution
The use of DNA methylation analysis at specific genetic loci to identify the source of body fluids through high-resolution melt analysis (HRM) or pyrosequencing, employing specific primers to amplify and determine methylation levels in genomic DNA from forensic samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If microscopic observation of sperms or histological staining of glycogen-rich cells is used to identify body fluids, then body fluid identification can be performed, but the reliability is low due to false positives and false negatives
Solution Approach 1:
The patent changes the detection parameter from morphological observation (microscopy) or chemical staining (glycogen detection) to DNA methylation status analysis. By detecting the methylation status of specific genomic loci that differ between body fluid types, the method achieves higher reliability and precision in body fluid identification, eliminating false positives and negatives associated with traditional methods
Solution Approach 2:
The patent replaces mechanical/morphological observation methods (microscopy) and chemical staining methods with molecular biology-based DNA methylation analysis. This substitution uses PCR amplification and methylation-specific detection to identify body fluids based on epigenetic markers, providing more accurate and reliable results
2Reliability
If RNA transcript analysis is used to identify body fluids, then body fluid identification can be performed, but additional sample processing is required which consumes the original sample
Solution Approach 1:
The patent makes DNA serve multiple functions: it is used both for body fluid identification (through methylation status analysis) and for subsequent suspect DNA comparison. By analyzing methylation patterns in the victim's DNA recovered from the suspect, the method identifies the body fluid source without consuming the sample, allowing the same DNA to be used for both identification and matching purposes
Solution Approach 2:
The patent performs body fluid identification as a preliminary step using DNA methylation analysis before proceeding to suspect DNA comparison. The methylation status determination is conducted on the victim's DNA recovered from the suspect, enabling forensic analysts to identify the body fluid source early in the analysis process without requiring separate RNA isolation
3Measurement precision
If DNA isolation is performed to compare suspect DNA, then suspect identification can be achieved, but the source of DNA cannot be identified
Solution Approach 1:
The patent segments the DNA analysis into two independent components: (1) body fluid source identification based on methylation status at specific genomic loci, and (2) suspect DNA comparison based on genetic sequence. This segmentation allows both pieces of information to be extracted from the same DNA sample simultaneously, preserving body fluid source information while performing suspect identification
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides a reliable, time- and cost-effective means to identify the source of body fluids with high sensitivity, requiring minimal sample processing and personnel training, and can differentiate between various body fluids even in mixed samples.
Implementation Method 1
conducting a PCR using the bisulfite treated genomic DNA as a template and one or more primer pairs designed to produce amplicons corresponding to the one or more of the genetic loci
Implementation Method 2
The level of methylation at specific loci in the genomic DNA isolated from a sample can be determined by high-resolution melt analysis (HRM) of amplicons produced using specific primers
Data Source
AI summary
The invention pertains to analyzing the levels of DNA methylation at specific genetic loci to detect specific body fluids, for example, vaginal secretions or vaginal epithelial cells, semen or sperms, saliva or buccal epithelial cells, or blood or blood cells. Particularly, the levels of methylation of DNA at the genetic loci corresponding to SEQ ID NOs: 1, 6, 11, and 16 are used to detect vaginal secretions or vaginal epithelial cells, semen or sperms, saliva or buccal epithelial cells, and blood or blood cells, respectively. The level of methylation at the specific loci can be determined by high-resolution melt analysis (HRM) or sequencing of the amplicons produced using specific primers designed to amplify the specific loci. Kits containing the primers and reagents for carrying out the methods disclosed herein are also provided.