Mitochondria are found by the hundreds in every human cell. They convert glucose to energy, and possess their own tiny genomes, separate and distinct from the organismal genome found in each cell nucleus.
That, and it comes in really handy when law enforcement officials state that the odds that they got the wrong guy are “one in a quadrillionzillion!”
In the mid-1990s, law enforcement added mitochondrial DNA comparison to its forensic genetic toolkit. Because there are so many mitochondria in each cell, readable copies of their genomes can often be found even when the nuclear genome has been damaged. This is especially useful for old, highly degraded biological samples.
Mitochondrial DNA-matching is based on the assumption that it doesn’t vary much in an individual: Aside from a few inevitable mutations, mitochondrial DNA are generally supposed to be the same in, say, heart cells and hair cells. But when Papadopoulos’ team applied the latest in gene-sequencing technology to mitochondrial genomes from nine tissue types in two people, that’s not what they found.
Instead, each person seemed to have a mixture of mitochondrial genotypes. One DNA variant, for example, was found in about 7 percent of a person’s skeletal-muscle mitochondria, but 90 percent of their kidney mitochondria. That spread was typical.
“It’s more than was thought, and was present in almost every tissue we looked at,” said Papadopoulos. Further research into these variations is needed, but forensic specialists should be careful to compare the same types of tissue, he said.
And don’t get me started on the practice of basing “evolutionary clocks” on the stuff.
Upon learning of the paper, John Planz, associate director of the DNA Identity Laboratory at the University of North Texas Health Science Center, cautioned that further studies are needed.
I’ll bet he did.
I remember reading a seemingly convincing paper that fingerprints weren’t exactly “all that” either.
Not that they weren’t useful, but that the usual “fingerprints are completely unique” was not necessarily true, especially when dealing with partials, and that studies that had shown uniqueness were not exactly above reproach statistically.
Might have been hokum, but I couldn;t judge, sounded plausible.
Then you add in crap like the FBI Forensics lab fiasco of a few years back and one confidence in experts tends to slip.
My favourite one is “no two snowflakes are alike”. Whoever came up with that bit of nonsense hasn’t done enough shoveling.
Let’s just build gigantic databases of everyone’s DNA, by, let’s say, making driver licensing conditional upon submitting a blood sample.
We can go even further and make it a law that every baby’s DNA sample, retina scan and fingerprint is taken upon birth.
That way we can randomly grab people in the streets and check whether they are in the country legally, if they have any o/s warrants or tickets and whether they are following restraining orders and bail/parole conditions.
We can swab books in the libraries to check who’s reading about explosives or poisons.
Having a comprehensive DNA/fingerprint/retina scan database will allow us to quickly weed out any criminal element, specially if we’ll couple it with retinal/fingerprint access control to every residence, wired to federal government. We’ll immediately know where Winston Smith is and what he is doing.
Some bacteria can engage in direct
swapping of genetic material. Among archaea such
interchanges are reportedly common –
which may not be relevant as the current best guess for the origin of
mitochondria is that they evolved from Proteobacteria. And it is well known that viruses
can modify genomes. One wonders about the extent
to which mitochondrion genetics could be influenced
by such processes. That might account for genetic
variation among mitochondria within an individual
higher organism, or some of it.
It really is caveat lector in regard to snippets
of information about research which are reported
in the popular press. My own rule of thumb before
even provisionally accepting a finding outside of
my own field is to wait until it has been severely, drastically criticised. If the finding
survives, then perhaps one can give it some credence.
AGW has notoriously flunked that test! At the first serious criticism it folded!
Me thinks Aaron has been watching too many re-runs of Minority Report.
Wow, this discovery could have a profound impact on a lot of recent research. Incredible.
Methinks Aaron was adding a point using a 1984 reference.
I’m not gonna make the obligatory O.J. Simpson joke. Someone else can.
B M
“””obligatory O.J. Simpson joke”””
I wasn’t wearing my GLOVE so I missed that one:-)))
The snowflake analogy was my first thought, as well. In the billions of years the earth has had snowfall, I’ll wager there have been billions of snowflakes exactly alike. I wouldn’t be surprised if a few of them contained the exact molecules of a different flake.
DNA works best when police and prosecutors have already decided who’s guilty. So do finger prints, and ballistic evidence. They can be used to exclude a suspect, but should never be considered a foolproof method of positive ID. I think most real courtroom evidence has nothing in common with the CSI type.
CSI programs are always showing cops matching bullets to a particular firearm. It doesn’t really work that way. If a recovered bullet was fired from a gun with a unique rifling, and a suspect owns a gun of that type, that’s one more piece of evidence. It doesn’t prove, conclusively, that the bullet couldn’t have been fired from any other gun, which came off the same assembly line.
All these forensic tools can do, is show that the suspect/defendant cannot be excluded, through DNA, ballistic, or fingerprint evidence, in most cases. It might be more convincing if all ten fingers match ten prints from a crime scene.
So, we -can’t- track Eve, mother of the entire living human race back by mitochondrial DNA to one lady in Africa 20,000 years ago? Awesome.
I always thought that story was BS but now its been proven to be BS. One more liberal “we are all brothers” junk science propaganda piece bites the dust.
In forensics, MtDNA is useful only for confirming whether a child is NOT the biological child. MtDNA is shared by many women and mutates slowly, thus most European and many N.A. immigrant women share the same MtDNA. All children have the MtDNA of their mother, but that MtDNA is also shared by many other people. I do see this as a useful forensic tool, but only to “exclude”, not confirm.
This is why my enthusiasm for the death penalty has been dropping for some time now. Reason mag has done an excellent job tracking disturbing abuses of forensic ‘evidence’. The US should consider a moratorium on the DP until there system is fit to pursue it.
Uhhh, Phantom, if you go back far enough, we are all still brothers as a common ancestor is an evolutionary inevitability.
Humm.. all this will be very interesting for the hiers of Anna Anderson, the lady in Virgina who claimed to be Anastasia Romanov. Her claim to be the youngest daughter of the last Tzar of Russia were denied because her mitochondrial DNA did not match that of Prince Phillip (related via their mothers).
I knew that this DNA swapping stuff was going on the first time I dropped by a Green Party convention.
cytotoxic, that argument assumes modern Homo Sapiens is the result of one breeding pair. I very much doubt this is the case. Mostly because I think we don’t understand evolution as well as some people say.
The Eve thing was a hypothesis based on mitichondrial DNA. wiki page isn’t too awful.
http://en.wikipedia.org/wiki/Mitochondrial_Eve
They have it at 200,000 years, not 20,000 as I previously said, but I still don’t like the idea because it relies too much on statistics and ignores other inconvenient truths, such as isolated breeding pools and the like.
My major objection is that its all just a little too pat, and I can’t believe Nature is so well understood. Seems I’m RIGHT again. Woo hoo!
I don’t believe in a lot of the jabber about Artificial Intelligence either, same reason. Marvin Minsky notwithstanding, I’m doubting anybody is going to crack that nut any time soon, if ever. It’d be pretty freakin’ cool for sure, but I think intelligence and self awareness and all that are a hell of a lot harder than ol’ Marvin says.
I mean, we can’t even predict what the stock market is going to do. Evolution and human neurology (and weather!) are orders of magnitude more complicated than that.