My mom thinks that there is DNA in human hair, I think she’s wrong. Can anyone shed light on this?
According to this paternity testing company’s website, a hair follicle pulled directly from the scalp is usable, but a hair that’s just fallen out in the course of normal events likely will not be.
However, this U.S. Department of Justice guide for collecting evidence in sexual assault cases indicates that most any kind of hair sample can be used.
The paternity test people do say using hair from a dead follicle is “difficult”, not necessarily “impossible”; it may just be more of a pain to do when, as in a normal paternity case, you should be able to get a clean sample, but worth trying for in a serious criminal case where the perpetrator hasn’t hung around to provide a nice convenient blood sample.
Another good reason to watch CSI!
It’s on Channel 5 Saturday 21.00 (followed by Law and Order - a fine crime double bill).
It’s not the hair strand that has the DNA, but the cells that are clinging to it. Depending on how it came out (pulled or fell) you may have more or fewer cells attached at the bottom. The more recently it fell out, the better condition the cells are in and, therefore, the better condition the DNA is in.
For related info, try Straight Dope Staff Report: Does your dandruff contain your DNA?
Yes but you must have the follicle, that is where the DNA cells are located.
In forensics the DNA is extracted from the root follicle at the base of the hair, which does contain live cells. So the only way to identify a person using their hair is to pluck it from their head with the follicle still attached.
Hair that simply breaks off isn’t viable for DNA testing because it doesn’t contain the follicle. Human hair weaves are made using hair that has been cut off rather than plucked with the follicle.
IIRC - as mentioned, the DNA is in the root of the hair.
However, in about the 1980’s there were a number of convictions based on hair comparison, and subsequently overturned by DNA evidence.
An “expert” would testify he had examined the evidence hair and a sample from the alleged perp and they were the same. One radio dramatization of one of these trials had the defence and the expert going incircles for several minutes:
“They are identical?”
“So how how are they different, if they are not identical?”
“They are not different”
Later, mass spectroscopy would also show basically no similarity in the samples. The amounts of trace elements, for example, would be completely different.
Hair is similar to fingernails. It is not alive, does not have cells, is just a hard secretion. But, buried in the chemstry of the hair/nails are trace amounts of various substances that the person had in their system when the hair was made by the cells. I.e. analysis of Napoleon’s hair showed that he had beeen slowly poisoned while in exile. http://news.bbc.co.uk/2/hi/europe/1364994.stm
As an addition, Hairs contain DNA, a sequence of molecules unique to each individual. DNA also can be found in blood and bodily fluids. Investigators try to match the DNA sequence in a hair sample found at a crime scene with a suspect’s DNA. DNA can also show how individuals are related to one another.
Do zombie hair follicles contain DNA? They are the “living dead” so I’m not sure what rules apply.
Some of the 9/11 remains have been identified from the hairs in the person’s hairbrush.
And a hair sample was used to create Nuclear Man in Superman 4.