Identification DNA Testing

Identification DNA Testing: Parentage, Forensics, and Genetic Fingerprinting

Synonyms

DNA Fingerprinting, Parentage Testing, RFLP Analysis for Parentage Evaluation, DNA Analysis for Genetic Identity, Paternity Testing

Test Commonly Includes

Utilization of polymorphic DNA regions to establish genetic identity or familial relationships with up to 99.99% accuracy.

Abstract

With the rise of DNA technologies and genome research, we now understand the human genome consists of ~120 million base pairs from 46 chromosomes. Each person inherits half of their DNA from each parent, but small genetic variations—especially at polymorphic regions—enable identification. DNA fingerprinting can determine identity, paternity, and familial relationships using 20–30 highly variable loci across the genome.

Patient Care / Preparation

No blood transfusions within 90 days prior to sample collection

Specimen

Whole blood (ACD or EDTA)
Tissue, semen, or cultured cells

Container

Blood: ACD or EDTA tube
Tissue: Sealed plastic bag, frozen at -70°C
Cell culture: T25 culture flasks

Collection

Tissue: 0.1–1 g, frozen immediately at -70°C
Blood: Maintain at 4°C; do not freeze
Cell cultures must be fully grown and sealed before transport

Storage Instructions

Tissue: Store and ship on dry ice or -70°C
Blood: Ship refrigerated at 4°C

Reasons for Sample Rejection

Thawed tissue or blood during transport
Insufficient sample quantity (<0.1 g)
Incorrect labeling or identification

Turnaround Time

2–4 weeks. DNA samples can be stored indefinitely.

Use

Establishes individual identity or biological relationships (e.g., paternity, siblingship, or criminal suspect identification) using high-resolution DNA analysis.

Limitations

Improper transport may damage DNA
Frozen/thawed blood yields poor DNA
Insufficient or degraded tissue limits analysis

Methodology

DNA is extracted using phenol-chloroform from WBCs, tissue, or cultured cells. It is then digested with restriction enzymes, electrophoresed, transferred to a nylon membrane, and hybridized with radioactive probes targeting polymorphic regions. Autoradiography reveals DNA banding patterns unique to each individual, except identical twins. This method can resolve parentage, zygosity, and forensic identity with extreme precision.

Additional Information

DNA fingerprinting has wide applications in:

Paternity and relationship testing
Military casualty and disaster victim identification
Resolving immigration disputes
Criminal investigations (rape, murder, etc.)
Medical cases of infant mix-ups or missing children

DNA remains constant across all tissues, making even forensic samples (blood, hair, semen) viable for analysis. Extreme care should be taken to prevent contamination.

References

Jacobs et al., Laboratory Test Handbook, Lexi-Comp Inc., 1994
Jeffreys AJ et al., Am J Hum Genet, 1991
Wolff RK et al., Genomics, 1988
Nakamura Y et al., Science, 1987
Gill P et al., Electrophoresis, 1987
McCabe ER, J Pediatr, 1992