As a field expert in the study of genetics and forensic science, I can provide a detailed explanation regarding the presence of DNA in hair and its relevance in DNA analysis.

Hair Structure and DNA Content
Human hair is a complex structure made up of a protein called keratin. It grows from hair follicles, which are tiny organs embedded in the skin. The hair shaft, which is the visible part of the hair, is composed of three layers: the cuticle, the cortex, and the medulla. The cuticle is the outermost layer and serves as a protective barrier. The cortex is the middle layer and contains the majority of the keratin fibers, while the medulla is the innermost layer and can vary in structure depending on the individual.

The part of the hair that has the highest potential for containing DNA is the hair follicle, particularly the bulb at the base of the follicle. This bulb is rich in cellular material, including the cells that produce the keratin proteins that make up the hair. These cells are metabolically active and contain the full complement of genetic material, which includes DNA.

DNA Analysis and Hair Collection
When it comes to DNA analysis, the method of hair collection is crucial. Hairs that have been naturally shed or broken off at the skin's surface do not contain the follicle and, therefore, do not contain DNA that can be used for analysis. The hair itself, once fully grown and pushed out of the follicle, is composed of dead cells and does not contain DNA. However, if a hair is plucked from the body, it will still have the follicle attached, and this follicle contains the living cells with DNA.

DNA Extraction and Testing
The DNA within the hair follicle can be extracted and used for various types of genetic testing. This includes paternity testing, forensic analysis in criminal investigations, and even medical testing for certain genetic conditions. The process of DNA extraction involves breaking open the cells within the follicle and isolating the DNA. Once extracted, the DNA can be amplified using a technique called Polymerase Chain Reaction (PCR), which allows for the detection of even small amounts of DNA.

Limitations and Considerations
It's important to note that while the hair follicle is a rich source of DNA, there are limitations to its use in DNA analysis. For instance, the quality and quantity of DNA can be affected by factors such as the age of the hair, environmental conditions, and the method of collection. Additionally, the DNA in the hair follicle can be contaminated with DNA from other sources, such as the person who collected the hair or the environment in which the hair was found.

In conclusion, while the hair shaft itself does not contain DNA, the hair follicle at the base of the hair does contain DNA-rich cells. This makes plucked hairs, with the follicle intact, a valuable source for DNA analysis. However, the process requires careful consideration of collection methods and potential sources of contamination to ensure accurate and reliable results.

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The hair follicle at the base of human hairs contains cellular material rich in DNA. In order to be used for DNA analysis, the hair must have been pulled from the body -- hairs that have been broken off do not contain DNA. Any body tissue that has not been degraded is a potential source of DNA.read more >>