Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: Mîn on 28/03/2004 14:52:00
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Hello! Could someone please explain me how DNA can be extracted from a fingerprint? How do you then compare it with other DNA samples? Thanks!
*MîN*
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Hi, I thought they get the DNA from the skin oils left with the fingerprint.
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when they say "DNA Fingerprinting" they don't mean they get the DNA from a finger print. They get it from any bodily reminants (blood, semen, hair etc.) that have DNA. (as far as I konw you wouldn't be able to get this from the skin oil either)
The reason it is called "fingerprinting" is because your DNA is unique to you, and thus can be used to identify you, just like your fingerprint.
The way they analyze the DNA is by using enzymes to cut the DNA at precise places. These enzymes cut the DNA strand every time they see a certain code in the DNA. Since all of our DNA is different, these codes apear at different places on the DNA for different people, so the bits and pieces of DNA left after the cutting are different lengths for different people. Therse lengths can be seen using a process called gel electrophoresis. simply put, the cut up DNA is put into the top of a jello-like sheet. A current is ran across the gel sheet. Since DNA is negatively carged it will be attracted to the positive end of the current, and it begins to move through the gell. Since the DNA has to snake its way through the tiny holes and pores in the gel-sheet. Because of this, the smaller pieces move faster than the big piecses, so if you run it for a given amount of time, the smaller pieces move farther than the big ones. If you add something to the dna that lets you see it, you will see a series of bands where all of the different sized pieces ended up when you turned the current off. By doing two smaples side by side, you can compare the banding pattern and see if they match (ie, a sample found at a crime scene, to a suspect in the crime).
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Here's an article which explains in simple terms about DNA fingerprinting and how to make DNA fingerprints :
http://www.thenakedscientists.com/HTML/articles/article/dalyacolumn8.htm
and here's a show we did featuring an interview with Professor Sir Alec Jeffreys who won the Nobel Prize for the discovery of the principle of genetic fingerprinting :
http://www.thenakedscientists.com/html/shows/2000.12.17.htm#interview
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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Thanks everyone!!!
*MîN*
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Oh yeah ! In year 10 I did two weeks of work experience in a biology lab at the ANU, it was really great. I got to do a lot of gel electrophoresis, and to demonstrate giving a bacteria a new gene, she put gave a colony a gene that made them blue instead of pink, because they were blue under their pink colouring or something and the gene cut in it and stopped them making pink. Or something. I also did a lot of pipetting from one set of tiny tubes to another, which wasn't so interesting :P In year 11 the class went to the science center to do gel electrophoresis, but it was with material that wasn't really all that good. By the way you put the DNA fingerprinting thing really really well, mr. Fly
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the pipetting from tiny tubes to tiny tubes can get to be VERY interesting.... you just have to know what you're pipetting and why.
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any cell of your body has your dna, so the dirt left form your fingers also contains deasd skin cells with DNA
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dirt from your fingers won't always have dead skin cells though
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DNA profiling is actually more accurate than fingerprinting. If a crime scene has a partial fingerprint it could still implicate hundreds of thousands of innocent people.
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I saw a program the other day about an American woman who gave birth to 2 kids with completely different dna to her. the social services in America believed they weren't her kids and went to court to do her for fraud and applied to remove the kids from her custody, it was only through the birth of her 3rd child that she was able to prove that they were hers.
it turns out she has two sets of different dna residing in her body , different parts of her body had different dna. It also turns out there are many people like her,so what does that say about using dna as a way to prove that someone committed a crime.
Michael
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quote:
Originally posted by ukmicky
I saw a program the other day about an American woman who gave birth to 2 kids with completely different dna to her. the social services in America believed they weren't her kids and went to court to do her for fraud and applied to remove the kids from her custody, it was only through the birth of her 3rd child that she was able to prove that they were hers.
it turns out she has two sets of different dna residing in her body , different parts of her body had different dna. It also turns out there are many people like her,so what does that say about using dna as a way to prove that someone committed a crime.
Michael
This has all sorts of interesting implications, not least with regard to evolution and inherited traits.
But with particular pertinence to this issue, it could cause false negatives, but would not cause false positives.
George
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They looked at another woman and it turned out her kids dna wise were not hers but half her husbands and half her brothers. i think they called her a chimera. weird but true
Michael
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quote:
Originally posted by ukmicky
They looked at another woman and it turned out her kids dna wise were not hers but half her husbands and half her brothers. i think they called her a chimera. weird but true
Michael
There was another woman whose kid's DNA was half hers, half the milkman's [:D]
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quote:
Originally posted by DoctorBeaver
quote:
Originally posted by ukmicky
They looked at another woman and it turned out her kids dna wise were not hers but half her husbands and half her brothers. i think they called her a chimera. weird but true
Michael
There was another woman whose kid's DNA was half hers, half the milkman's [:D]
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you should have said postman,it would have added a bit of credance to your story
Michael
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Postman? Don't make me laugh. We don't get them around here!
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