The half life of DNA is roughly 521 years [1]. The sample was 99 million years old, so you could expect roughly 3.33347 × 10^-57200 [2] percent of the DNA to be left. And considering humans have about 7 billion base pairs [3], you could reasonably expect no real recoverable information to remain.
In what sense does DNA have a half-life? It can't be radioactivity so is it seems to be just about molecular disintegration? Which is weird because why should a stable structure have a half-life?
The introduction of the first citation explains it a little bit:
> DNA has limited chemical stability and decays without the enzymatic repair mechanisms of living cells [18]. Following cell death, nucleases start to cleave the DNA into fragments [19] and during decomposition, the DNA is digested by micro-organisms [18,20]. In determining long-term DNA decay, it is believed that hydrolysis of amino groups accelerates the loss of purine residues (depurination), resulting in strand cleavage [21,22]. This random DNA fragmentation generates a characteristic negative exponential correlation between DNA fragment length and number of molecules (figure 1a) [23,24,26,27].
Thanks! I even clicked on the link and read every sentence that had "half" in it but didn't see anything... didn't expect it to be somewhere else in the introduction haha.
> As a general rule, it's safe to assume every word in the abstract of a paper is significant.
...what? The sentence quote above was from the introduction, not the abstract. Nothing in the abstract answered my question of why a stable structure like that of DNA should undergo disintegration. (Did you read the abstract yourself?)
To be fair, many of those processes are things that I would presume halt at some point in an isolated chemical environment.
Also, what kind of breakdown? If segments up to a certain sizer were stable, that would be enough to reconstruct a full genome of the sequencers were sensitive enough and the final segments long enough.
This link might help answer your questions. Also, half-life in this context is just referring to how long it takes the number phosphodiesterase linkages (bonds holding the DNA backbone together) to decrease by 1/2. Half-life can refer to other types of decay as well :-)
DNA has a half life, but the real question here is how being trapped in amber would affect that half life. So there may be more - or less - than one would expect if the DNA would be in some other environment. At a guess the time span involved is long enough that no matter how this would be influenced there still would not be any usable DNA fragments.
Another question is what sort of artifacts would sequencing material in amber produce. Considering the quality of data from formaldehyde fixed paraffin embedded (FFPE) samples I think it would be quite a struggle
Proton decay is not a feature of the standard model, it comes from other theories with far less experimental evidence behind them; by no means at this point can we say that protons "have" a half-life.
It really depends; entropy is a harsh mistress. The output of a paper shredder can theoretically be reformed into the source paper, but below a certain size fragment there's not enough information left to recover.
I didn't do it, but I'm going to guess that it was because your comment gave absolutely no context or meaningful input, and it therefore seems reasonable that someone has decided that it adds no value to discussion of the article.
The most interesting part to me is that there are feathers trapped inside the amber:
> The amber, which weighs 6.5 grams, contains bone fragments and feathers, adding to mounting fossil evidence that many dinosaurs sported primitive plumage...
Indeed, and a fairly recent discovery among Velociraptors.
> The feathers of the flightless Velociraptor may have been used for display, for covering their nests while brooding, or for added speed and thrust when running up inclined slopes.
The assumption right now is that every theropod had feathers of some kind somewhere. Some of them may have lost them as adults, or only be partially covered, the skin impression information is somewhat inconsistent. But generally yes, theropods looked very much like big carnivorous flightless birds, plumage and all. Velociraptor for instance likely had what today we would describe as wings.
The most recent Jurassic Park movie has a solution to this problem. In it they say that they had to use genes from amphibians together with the dinosaur genes in order to create their animals. This way the issue is reconciled.
Now that I think of it, they mentioned the amphibian DNA in the first one (and the book), too, to explain why the dinosaurs were suddenly able to procreate.
Still, a life-size velociraptor ot T-Rex covered in a coat of feathers must be quite a sight.
"T. Rex Was Likely Covered in Scales, Not Feathers"
What I don't understand is how something the size of T rex doesn't just die from heat shock whenever it breaks into a sprint. I vaguely recall reading somewhere that one of the dangers facing beached whales is that they start to overheat rapidly. Did big dinosaurs just live in cooler environments? Do they have better ways to dissipate heat? Did they like dipping in lakes and ponds? I'm sure someone would have asked these questions already, but no idea what current thinking in the field is...
Whales have a lot of fat (and I'm assuming other insulating tools) to keep them warm in cold water, their bodies aren't designed to be beached in warm air under the sun. Elephants, while not as large as a trex, can survive the hot African savanna no problem so I feel evolution could handle making a trex live in moderate temperatures without to much of a problem
Life-size velociraptors were apparently about turkey-sized. There were others in the same family that were larger, and a bit more similar to the animals depicted in the book/movie.
Possibly. Or maybe it was only the dinosaurs in this group, the theropods, that had them. Or that had them to a significant degree.
I still picture the giants being featherless, just as modern elephants, rhinos, and hippos, are hairless, or mostly hairless, with only a few coarse bristles. I am not, however, aware of anything in the literature on this topic, so I have no evidence to offer.
It is interesting that drawings of Chinese dragons always have something like feathers, while European dragons do not. Dragons may have at least partly been inspired by dinosaur fossils.
are we talking both two and four leg variety or just the two legged variety? It ispossible those with smaller forelegs/arms were more avian, perhaps even having given up the wings for more useful appendages
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[ 3.6 ms ] story [ 92.1 ms ] threadFrom the article: “McKellar said that soft tissue and decayed blood from the tail were found in the amber but no genetic material was preserved.”
[1] http://rspb.royalsocietypublishing.org/content/early/2012/10... [2] https://www.wolframalpha.com/input/?i=0.5%5E(99+million+%2F+... [3] https://en.wikipedia.org/wiki/Human_genome
> DNA has limited chemical stability and decays without the enzymatic repair mechanisms of living cells [18]. Following cell death, nucleases start to cleave the DNA into fragments [19] and during decomposition, the DNA is digested by micro-organisms [18,20]. In determining long-term DNA decay, it is believed that hydrolysis of amino groups accelerates the loss of purine residues (depurination), resulting in strand cleavage [21,22]. This random DNA fragmentation generates a characteristic negative exponential correlation between DNA fragment length and number of molecules (figure 1a) [23,24,26,27].
...what? The sentence quote above was from the introduction, not the abstract. Nothing in the abstract answered my question of why a stable structure like that of DNA should undergo disintegration. (Did you read the abstract yourself?)
Also, what kind of breakdown? If segments up to a certain sizer were stable, that would be enough to reconstruct a full genome of the sequencers were sensitive enough and the final segments long enough.
https://www.nature.com/news/dna-has-a-521-year-half-life-1.1...
https://en.wikipedia.org/wiki/Proton_decay
https://en.wikipedia.org/wiki/Exponential_decay
Or is there something fundamental I'm not aware of?
I did downvote this one though, because of the antepenultimate entry in https://news.ycombinator.com/newsguidelines.html
> The amber, which weighs 6.5 grams, contains bone fragments and feathers, adding to mounting fossil evidence that many dinosaurs sported primitive plumage...
> The feathers of the flightless Velociraptor may have been used for display, for covering their nests while brooding, or for added speed and thrust when running up inclined slopes.
https://en.wikipedia.org/wiki/Velociraptor#Feathers
http://science.sciencemag.org/content/317/5845/1721
http://www.cell.com/current-biology/fulltext/S0960-9822(16)3...
"A Feathered Dinosaur Tail with Primitive Plumage Trapped in Mid-Cretaceous Amber"
https://www.google.co.nz/amp/photofunonline.com/photographer...
Would be interesting to see a remake that used all of the current knowledge about dinosaurs, what they looked and behaved like.
Still, a life-size velociraptor ot T-Rex covered in a coat of feathers must be quite a sight.
"T. Rex Was Likely Covered in Scales, Not Feathers"
What I don't understand is how something the size of T rex doesn't just die from heat shock whenever it breaks into a sprint. I vaguely recall reading somewhere that one of the dangers facing beached whales is that they start to overheat rapidly. Did big dinosaurs just live in cooler environments? Do they have better ways to dissipate heat? Did they like dipping in lakes and ponds? I'm sure someone would have asked these questions already, but no idea what current thinking in the field is...
Jurassic Park lied to me twice
Next thing, somebody will point out that there are no 12-year-old girls that routinely use SGI workstations. :.-(
I still picture the giants being featherless, just as modern elephants, rhinos, and hippos, are hairless, or mostly hairless, with only a few coarse bristles. I am not, however, aware of anything in the literature on this topic, so I have no evidence to offer.
The feathered dinosaur fossils have first been discovered in Liaoning, China (and apparently many others in Asia): https://en.wikipedia.org/wiki/Feathered_dinosaur#Fossil_disc...
Maybe evolution made some differences.
(disclaimer: I do not know the actual scientific literature)