Precautions in collecting DNA from hair

Summary of this article

When collecting DNA from hair, the number required depends on the situation and the testing method, but basically, hair with the root (hair follicle) attached is important; DNA is mainly contained in the hair follicle, so it is difficult to obtain a sufficient amount of DNA from a section of hair (hair trunk) that has been cut off.

About the number of units required

Rooted hairs: Usually, 5 to 10 rooted hairs are sufficient to extract a sufficient amount of DNA. Some laboratories may recommend a larger number of hairs, but at least five hairs will provide adequate results in most cases.
Hair without roots (hair trunk only): When hair roots are absent, mitochondrial DNA (mtDNA) must be used for analysis because nuclear DNA can hardly be obtained from the hair trunk. Because mitochondrial DNA is abundant in hair trunks, even when mitochondrial DNA is used, more than 20 hairs may be required, depending on the quality of the specimen.

Conclusion:

Depending on the purpose and method of DNA analysis, five to ten hairs with roots are often sufficient. In the case of hairs without roots, mitochondrial DNA rather than nuclear DNA will be analyzed, and more hairs may be needed.

It is important to check with each laboratory in advance as the number of recommended units may vary.