As a geneticist with extensive experience in DNA analysis, I can provide a comprehensive answer to your question about DNA testing from hair. It's important to clarify that DNA testing from hair is possible, but with certain limitations and considerations.

First and foremost, understand that there are two key parts of a hair for DNA purposes: the root and the shaft. The root, which is attached to the scalp, contains a follicle that houses a significant amount of cellular material, including nuclear DNA. This is the type of DNA that is used for most DNA tests, including paternity and ancestry tests. It contains the genetic information that is unique to each individual, except for identical twins.

On the other hand, a hair shaft simply doesn't contain nuclear DNA. It's made up of a protein called keratin and does not have living cells that would contain the individual's DNA. Therefore, without the root or the follicle, you cannot perform a standard nuclear DNA test on a hair shaft alone.

However, there is a type of DNA that can be extracted from a hair shaft: mitochondrial DNA (mtDNA). Mitochondrial DNA is different from nuclear DNA in several ways. It is inherited solely from the mother, and it is not unique to each individual. Instead, all maternal relatives share the same mtDNA sequence. mtDNA testing is typically used in cases where nuclear DNA is not available, such as in ancient remains or when identifying remains in a disaster where the body is severely damaged.

To perform mtDNA testing on hair, the hair must be properly collected and preserved. The process involves several steps:


1. Collection: The hair should be collected by pulling it out from the root, ensuring that the follicle is attached. This is crucial because the follicle contains the necessary cellular material for DNA extraction.


2. Preservation: The hair sample must be kept in a sterile and dry environment to prevent contamination and degradation of the DNA.


3. Extraction: The DNA is then extracted from the follicle using a chemical process that breaks down the cells and releases the DNA.


4. Amplification: The extracted DNA is amplified using a technique called Polymerase Chain Reaction (PCR), which makes millions of copies of the DNA so that it can be analyzed.


5. Analysis: The amplified DNA is then analyzed using various methods, such as sequencing or restriction fragment length polymorphism (RFLP), to determine the mtDNA sequence.


6. Interpretation: The results are compared to known mtDNA sequences to identify the individual or to establish a maternal relationship.

It's important to note that while mtDNA testing can provide valuable information, it has its limitations. Since mtDNA is inherited maternally, it cannot establish a direct biological relationship between a child and a father. Additionally, because all maternal relatives share the same mtDNA, it cannot be used to distinguish between individuals who share the same maternal line.

In conclusion, while DNA testing from hair is possible, it is limited to mtDNA testing and requires the hair to be collected with the root and follicle attached. The process is complex and requires specialized equipment and expertise. It is not a substitute for standard nuclear DNA testing, but it can be a valuable tool in certain circumstances.

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First and foremost, understand that there are two key parts of a hair for DNA purposes. ... And a hair shaft simply doesn't contain nuclear DNA. In other words, you can only do one of the three types of DNA testing on a lock of hair that doesn't have a root or follicle attached, and that's the mtDNA testing.Jun 3, 2012read more >>