Hair itself is not a reliable source of DNA for testing. While hair can contain DNA, it's primarily found in the root, not the shaft. Successfully extracting viable DNA from hair depends heavily on the presence of follicular tissue attached to the root and the proper collection method. Therefore, hair DNA testing isn't the preferred method due to its low success rate and unreliability.
Why Hair DNA Testing Is Problematic:
- Limited DNA: The hair shaft contains minimal DNA. The majority of usable DNA resides in the root's cells. If the root is damaged or missing, the DNA yield is significantly reduced or nonexistent.
- Low Success Rate: Even with intact roots, success rates for extracting usable DNA from hair are often below 60%, according to various sources. The success heavily depends on proper collection and handling.
- Alternative Methods: Other methods, like obtaining samples of blood or saliva, are much more reliable and efficient sources of DNA for testing.
Types of DNA Found in Hair:
- Nuclear DNA: This is the primary type of DNA used in most genetic tests (ancestry, paternity, forensics). It's located in the root and offers the most comprehensive genetic information.
- Mitochondrial DNA (mtDNA): This type of DNA is found in the hair shaft and can be useful for tracing matrilineal ancestry (mother's side). However, it provides less information than nuclear DNA.
Improving the Chances of DNA Extraction from Hair:
- Proper Collection: Hair samples should be carefully collected to preserve the root and surrounding follicular tissue. Pulling hair out by the roots significantly increases the chances of obtaining enough DNA.
- Storage: Store hair samples in a dry, cool environment to prevent DNA degradation. Paper envelopes and airtight containers with desiccants are often recommended.
In Conclusion: While hair can potentially contain DNA, primarily in the root, its use for DNA testing is generally unreliable and not recommended. Other sources offer far superior results.
