A DNA test using a hair sample offers a non-invasive option for genetic analysis, especially when other sample types like buccal swabs or blood are impractical. This method provides genetic information for purposes such as paternity testing or establishing ancestral connections. Its success largely depends on the hair sample’s characteristics and meticulous collection.
Essential Hair Sample Characteristics
For DNA analysis, a hair sample must contain the hair follicle, or root. The hair shaft, the visible part of the hair strand, contains very little nuclear DNA, which is needed for most identity-based genetic tests. The shaft primarily holds mitochondrial DNA, useful for maternal lineage studies but less informative for individual identification. The follicle, a bulb-like structure at the base of a freshly pulled hair, contains the necessary nuclear DNA.
Hairs that have naturally fallen out or been cut usually lack the root and are unsuitable for nuclear DNA extraction. Laboratories typically require 5 to 10 hair strands, each with an intact root. This root provides the cellular material for genetic extraction and analysis.
Collecting Hair for DNA Analysis
Proper collection techniques ensure a hair sample contains the necessary genetic material and remains free from contamination. To obtain a viable sample, hair strands should be carefully pulled from the scalp, rather than cut, to ensure the root remains attached. Pulling hair from different areas of the scalp is often recommended to increase the likelihood of collecting strands in the anagen or growing phase, which typically have more robust roots.
Before collection, hands should be thoroughly washed, and clean tweezers or a clean tissue should be used to handle the hair. The root end of the hair should never be touched directly, as this can introduce contaminating DNA from the collector or other sources. Each collected strand should be placed immediately into a clean, dry paper envelope, avoiding plastic bags which can trap moisture and promote degradation. Each individual’s sample should be kept separate to prevent cross-contamination.
Submitting Samples and Interpreting Findings
Hair samples should be air-dried if there is any visible moisture, then sealed in a paper envelope and labeled with the individual’s name and the collection date. Many laboratories provide specific collection kits with pre-labeled envelopes and instructions for proper handling and submission. Prompt submission helps preserve DNA integrity, although hair samples can remain viable if stored correctly in a cool, dry place.
At the laboratory, scientists extract DNA from the hair follicles, often using Polymerase Chain Reaction (PCR) to amplify the tiny amounts of genetic material present. Turnaround time for results varies from a few days to several weeks, depending on the laboratory’s workload and the complexity of the test. Results are usually communicated securely, detailing the genetic matches or profiles obtained, for purposes like determining biological relationships or tracing ancestry.
Considerations for Accurate Results
The success and accuracy of a DNA test from hair samples depend on the quality and quantity of the DNA obtained. Insufficient DNA, often due to a missing intact root or too few strands, is a common reason for test failure. Even with seemingly intact roots, the amount of viable nuclear DNA can vary significantly between individuals and even between strands from the same person.
Environmental factors also play a substantial role in DNA degradation. Exposure to heat, humidity, sunlight, or certain chemicals can damage DNA molecules, making extraction and analysis challenging or impossible. Proper collection and storage methods are important to minimize exposure to elements that can compromise the sample’s genetic integrity. Understanding the specific requirements and limitations of hair DNA testing is crucial for obtaining reliable outcomes.