Long D13S317 variant allele: a cautionary case report

Area of Science:

• Forensic genetics
• Human identification
• Population genetics

Background:

• Kinship analysis and parentage testing rely on accurate DNA profiling.
• Short tandem repeat (STR) loci are commonly used for genetic identification.
• Allelic dropout and other artifacts can complicate interpretation of STR profiles.

Observation:

• An unusual pattern at the D13S317 locus in a father-child kinship case suggested a silent allele.
• Investigation using multiple commercial STR kits revealed the pattern was due to a single long variant allele.
• The variant allele exhibited overlapping amplification with different loci across various kits.

Findings:

• Sequencing identified a duplication within the D13S317 locus as the cause of the long variant.
• This duplication created an unintended binding site for a short amplicon reverse primer.
• The variant allele's characteristics led to potential misinterpretation of genotyping results.

Implications:

• Accurate interpretation of forensic genetic data is crucial for legal and identification purposes.
• The characterized D13S317 variant highlights the need for careful analysis of complex STR patterns.
• Awareness of such variants can improve the reliability of DNA testing and kinship analysis.