If DNA is made up of just 4 bases, then surely by definition there are only so many variations? Admitedly - Trillions if not more, but surely this means but one day people will have the same DNA?

Does this not totally undermine the idea of using DNA in a criminal sense? And surely the same also applies to fingerprints?

AFAIK DNA evidence alone is not sufficent to prove something beyond reasonable doubt in the UK anyway.

The chances of two humans having the exact same DNA strings are so small it's unbelieveable. Even with ginetic engineering in the future it's massively unlikely any two people end up the same. And even if they did, they'd probably never meet.

Identical twins have the same DNA, don't they? And, it doesn't completely invalidate using DNA as evidence. But, maybe in the future there may be clones everywhere, so that may be a problem. At that point they'll probably just start microchipping newborns.

Do your own homework.

IIRC the chances of identical DNA is so remote that DNA can be trusted as a 'unique ID' for people, obviously identical siblings are an exception here.

Edit: @W4H, I imagine by the time there are clones about the place, they will genetically engineer some sort of serial/batch number into them.

Quote from Some guy on Yahoo! Answers (Good enough for me...) :

Yes it can, and depending on the DNA sequencing technque and the ancestry of the peole involved it might be quite high.

Remember criminal DNA sequencing doesn't test the whole genome. It only tests a tiny fragment, less than 0.01%. It is estimated that the chances of even such a tiny fragment matching the worng person are less than 1 in a million, but studies over the past few years have indicated that certain populations, such as some Jewish groups, may have much higher chances of random matches.

Even at 1 in million that means thatin a major city like New York or Los Angeles there may be a dozen peole walking arund who match you perfectly.

In practice people don't get indicted or convicted on the basis of DNA alone. There has to be some other evidence linking them to the crime, even if only circumstancial. Aside from that the law in the US only requires level of proof beyond reasonable doubt. A doubt of less than one in a million is way below the reasonable level.

Link.

I would like to hear Lerts' opinion on this....

'tis not homework, just been arguing with a teacher about it

I know the odds are low, but in "the common mind" DNA is irrefutable and unique, when actually it's really not...

Quote from Jakg :

I know the odds are low, but in "the common mind" DNA is irrefutable and unique, when actually it's really not...

The thing about popular truth is that in a lot of cases it's not true.

Argue a case for it all you like Jack, you'll never be as so damned fantastic as I am *pout*.

Quote from Becky Rose :

Argue a case for it all you like Jack, you'll never be as so damned fantastic as I am *pout*.

Wait, what?

Disclaimer - I have not raped, murdered or stolen - This is just out of curiousity!

You're calling me a murdering rapist thief? o.O

Gosh, if you think that what do my enemies think of me....

I wasn't saying that?

Forensic science has totally ruined murdering. Not to mention crime fiction. I saw a cop show on TV the other day - it consisted of people in white coats looking into microscopes for about an hour.

Another interesting hole in DNA fingerprinting is chimerism, as in the case of Lydia Fairchild. She appeared to have differents sets of DNA in her tissues, and tests indicated that she was not the mother of her children.

Apparently, a halibut has a 98% identical genetic code to us humans, and a banana is about 92% identical. So maybe one day they'll be robbing banks and mugging little old ladies...that'll be and interesting Crimewatch reconstruction

Quote from amp88 :

In practice people don't get indicted or convicted on the basis of DNA alone. There has to be some other evidence linking them to the crime, even if only circumstancial. Aside from that the law in the US only requires level of proof beyond reasonable doubt. A doubt of less than one in a million is way below the reasonable level. Link.

The problem with that of course is that, (unlike fingerprints even), DNA is transferable. In fact it is entirely this property of DNA that allows it to be used as evidence in the first place, but it is also exactly the property of DNA as evidence that makes it so fallable as evidence. There are a lot more innocent methods of transfering DNA on to an object than there are non innocent ones. To my mind DNA should only form part of the physical evidence against a person, to use it as the only form of physical evidence is entirely unjust IMO.

This is where DNA evidence has fallen down in the past, (and probably will continue in the future too), so much so that a couple of relatively high profile cases that were reversed on appeal were supposed to lead to a review of all other cases where DNA alone had been used to convict someone. As far as I am aware this hasn't happened. A situation that can't be tollerated IMO.

http://www.housemag.co.uk/inde ... %5D=92&type=editorial

Quote from Mazz4200 :

Apparently, a halibut has a 98% identical genetic code to us humans, and a banana is about 92% identical. So maybe one day they'll be robbing banks and mugging little old ladies...that'll be and interesting Crimewatch reconstruction

Wow, so it'll be a banana robbing a bank with a banana stuffed inside a hoodie. :o

Amazing that such a small % of genetic code makes such a big difference.

It's a small percentage, but still probably enough data to fill several encyclopedias.

Quote from S14 DRIFT :

Wow, so it'll be a banana robbing a bank with a banana stuffed inside a hoodie. :o

Amazing that such a small % of genetic code makes such a big difference.

Well no, that would be like a midget holding up a bank with another midget shoved inside a sock.....erm....the banana will probably have a sawn-off shotgun, and a stocking over his head....erm

Yeah, it is amazing how such a small change in a genetic code can make such huge difference to the end result. There are quite a few colarge's (sp?) on the net of different fetuses in early development, and you'll be hard pushed to tell which one becomes a human from one that ends up a horse, or a mouse, or a Max Mosely. Not got the time right now to hunt for it, but will post it when i can.

Quote from tristancliffe :

It's a small percentage, but still probably enough data to fill several encyclopedias.

There was one of those weird and ultimately useless statistical fact type things about that not so long ago. I can't remember the details of it, but it was something like. If you took all the stored information in just one single DNA thingy, and downloaded it into a load of modern day supercomputers with the biggest hard drive available, you could stack them up as far as the moon and back, and still not have enough space to store all the information.

Don't understand it myself, and i'm not even sure if it's true, but i guess statisticians have to earn a living somehow.

Quote from tristancliffe :

It's a small percentage, but still probably enough data to fill several encyclopedias.

Well I have always wanted to right click a human and select "edit" to open up it with NotePad and see the code inside.

Or a banana.

Quote :

Well I have always wanted to right click a human and select "edit" to open up it with NotePad and see the code inside.

Quote from becky Rose :


<php (people Homosapiens Program)
If( Dna=='human' ){
Fabricatesocialconstructandstartwars=true;
Taxtheeatsleepsexperogative=true;
}
Else {
Followeatsleepsexperogative=true;
}


Pmsl

Quote from Mazz4200 :

If you took all the stored information in just one single DNA thingy, and downloaded it into a load of modern day supercomputers with the biggest hard drive available, you could stack them up as far as the moon and back, and still not have enough space to store all the information.

thats a total complete load of rubbish
according to wikipedia the human genome project found that the entire human dna consists of 3.08 billion base pairs
each of those pairs can in principle be any of 4 possible combinations of bases... in other words a base pair stores 2 bit
take all that and you end up with about 734 megabyte of data... so the whole thing almost fits on a single cd