While direct-to-consumer paternity tests typically rely on buccal (cheek) swabs, it is scientifically possible to use hair samples for DNA analysis. This method involves specific considerations, as the quality and type of hair collected are important for obtaining accurate results.
How DNA in Hair is Used for Paternity Testing
The scientific basis for using hair in paternity testing lies in the presence of nucleated cells, which contain an individual’s nuclear DNA. Nuclear DNA is passed down from both parents, making it suitable for establishing biological relationships. The hair shaft itself does not contain sufficient nuclear DNA for typical paternity analysis, as it is primarily composed of keratin.
For a hair sample to be viable, it must include the hair follicle or root. This root, often visible as a small white bulb at the end of a pulled hair, contains the necessary nucleated cells. Once collected, DNA is extracted from these cells in a laboratory setting. This process often involves techniques like polymerase chain reaction (PCR) to amplify the small amount of DNA present, creating enough material for analysis. The extracted DNA is then analyzed and compared to DNA markers from the child and, if available, the mother, to determine a probability of paternity.
Important Factors for Hair Sample Paternity Tests
Obtaining viable hair samples for paternity testing requires specific collection guidelines. Hair strands must include the root or follicle, as this is where the necessary nuclear DNA resides. Hairs that have shed naturally or been cut lack this root, making them unsuitable for DNA analysis. Therefore, hairs must be pulled directly from the scalp or body to ensure the root is intact.
To increase the likelihood of successful DNA extraction, laboratories recommend collecting 5 to 10 hairs with roots per person. The quality of DNA from hair can vary and is more susceptible to environmental contamination and degradation compared to other sample types. Exposure to chemicals, hair treatments, or other environmental factors can compromise DNA integrity, potentially making it difficult to obtain a usable DNA profile. Proper storage in a clean, dry paper envelope, rather than plastic, is also important to maintain sample integrity.
Comparing Hair Samples to Other Testing Methods
While hair samples can be used for paternity testing, they are generally considered less reliable and more challenging to process than other common methods. Buccal (cheek) swabs are widely regarded as the industry standard for paternity testing. This preference stems from their ease of collection, as a simple swab of the inner cheek is non-invasive, painless, and can be done quickly for individuals of all ages.
Buccal swabs consistently yield a high quantity and quality of DNA, leading to more accurate and conclusive results. The cells collected from the cheek are less prone to environmental contamination and degradation because they are protected inside the mouth. Blood samples are another highly accurate method, providing substantial amounts of DNA, though their collection is more invasive than a buccal swab. The high DNA yield, lower contamination risk, and straightforward collection process make buccal swabs the preferred and most cost-effective option for most paternity tests.