Recently i came across an article on DNA barcoding.
My English is bad (i am not native), and perhaps i misunderstood something…
So, is it true, that 90% of animals have an UNIQUE 600bp DNA sequence in their mitochondrial genome?
From what i could understand, this relatively short DNA sequence (COI) is what the DNA barcoding is based on. DNA barcoding is used by scientists and also in everyday life to identify species (e.g. what kind of meat is in your hamburger). At this moment there are 100,000 species in DNA barcode database (and counting)
It looks like the Bible was right “And God made the beasts of the earth according to their kinds…”, moreover, it seems like our Creator put a barcode on each of it…
I don’t know why you think the mito genome is a “very fragile thing” or why this would matter for COI barcoding. (It doesn’t.)
Your question “how did this happen?” seems to presume that the existence of unique sequences in COI is remarkable. I’m not sure that it is. My understanding of the COI barcode is that it was chosen by humans based on the fact that it is ubiquitous because COI is a basic gene required in all living things (that have mitochondria, which of course excludes the vast majority of Earth’s living things, but that’s not important here). The 600-bp region is easy to amplify by PCR, and that was a key technical aspect when species barcoding was first proposed 15 years ago. I think that the gene was already known to exhibit substantial diversity between species. In other words, at first glance, the COI barcode is just a convenient way to look at species-specific DNA sequences for identification purposes. The existence of species-specific DNA sequences by itself is not surprising or interesting, and requires no special explanation other than some measure of reproductive isolation and, of course, common descent from some founding population.
However, I just looked at a recent paper that argues that COI is a particularly good choice, because it is biologically relevant to speciation itself. That is cool and interesting, because speciation genes are cool and interesting, and it seems to imply that the COI barcode was a great idea. But if you read the paper, you’ll see that there is debate and uncertainty surrounding COI as a barcode. I think this is unsurprising, simply because biology and population genetics can be a little too complicated for something as simple as a “barcode” for a species. It’s a great idea, and a useful tool, but not a singular proof or something like that.
If you think that “common ancestry is based on DNA sequence similarities” alone, then you haven’t read the most basic facts about phylogenetics. Which makes discussion with you on that topic pointless.
Nice article, thanks for sharing it! It was very interesting.
But you have misunderstood it. The authors are not trying to understand why there are species-specific DNA sequences. That’s not interesting at all, by itself. They are trying to understand why mitochondria, in particular, seem to track with species and speciation. This is what I already mentioned as interesting, in a post above.
“New work by a pioneering scientist details how subtle changes in mitochondrial function may cause a broad range of common metabolic and degenerative diseases.”
“The discrete changes in nuclear gene expression in response to small increases in mitochondrial DNA mutant level are analogous to the phase changes that result from adding heat to ice,” said Wallace. “As heat is added, the ice abruptly turns to water and with more heat, the water turns abruptly to steam.” Here a quantitative change (an increasing proportion of mitochondrial DNA mutation) results in a qualitative change (coordinate changes in nuclear gene expression together with discrete changes in clinical symptoms)."
That article isn’t about mito genome fragility, and the quotes you provide don’t have anything at all to do with mito genome fragility. Wouldn’t it be better to learn more before posting all this stuff? Just a thought.