What method is commonly used to determine if a stain is human or non-human DNA?

What method is commonly used to determine if a stain is human or non-human DNA?

• A. Visual inspection of stain color.
• B. ELISA assay for human-specific proteins.
• C. PCR-based species identification targeting mitochondrial or nuclear sequences.
• D. Chloroplast DNA sequencing.

Answer: (C)

Determining the species origin of DNA in a stain relies on detecting sequence differences between humans and other species by using PCR to target human-specific DNA regions. This approach is powerful because it can specifically amplify human DNA even when the stain contains mixed or degraded material. Targeting mitochondrial DNA or human nuclear markers gives high sensitivity (mitochondrial DNA is present in many copies per cell) and high specificity (primers can be chosen to amplify only human sequences). In practice, a positive human-specific amplicon indicates human DNA, and sequencing the product can confirm the exact species by comparison to reference sequences. Visual inspection of stain color isn’t reliable for identifying DNA origin. An ELISA assay detects proteins, not DNA, and even if it detects human proteins, it doesn’t directly establish the DNA’s species source. Chloroplast DNA sequencing would identify plant DNA, not human DNA, and isn’t suitable for determining whether a stain is human or non-human DNA.

Determining the species origin of DNA in a stain relies on detecting sequence differences between humans and other species by using PCR to target human-specific DNA regions. This approach is powerful because it can specifically amplify human DNA even when the stain contains mixed or degraded material. Targeting mitochondrial DNA or human nuclear markers gives high sensitivity (mitochondrial DNA is present in many copies per cell) and high specificity (primers can be chosen to amplify only human sequences). In practice, a positive human-specific amplicon indicates human DNA, and sequencing the product can confirm the exact species by comparison to reference sequences.

Visual inspection of stain color isn’t reliable for identifying DNA origin. An ELISA assay detects proteins, not DNA, and even if it detects human proteins, it doesn’t directly establish the DNA’s species source. Chloroplast DNA sequencing would identify plant DNA, not human DNA, and isn’t suitable for determining whether a stain is human or non-human DNA.