Surviving 65 Million Years: Dino-DNA Explained

[Mentat]

I don't know very much about cytology or molecular biology (high-school level, and a few supplementary bits of literature), so maybe this is a stupid question, but: How did any useful DNA manage to survive 65 million years?

Apparently, we have some dino-DNA, and I'm just wondering how it could have stayed intact (or even nearly so) over 65 million years of global change, local weathering, etc.

 

[Mentat]

I don't know very much about cytology or molecular biology (high-school level, and a few supplementary bits of literature), so maybe this is a stupid question, but: How did any useful DNA manage to survive 65 million years?

Apparently, we have some dino-DNA, and I'm just wondering how it could have stayed intact (or even nearly so) over 65 million years of global change, local weathering, etc.

Just to avoid misunderstanding: when I say "we have some dino-DNA", I just mean that we have collected samples of such DNA.

 

[Monique]

Useful DNA stays intact simply because if it didn't, the organism would die (or at least have a survival disadvantage).

It's called DNA conservation, you can compare genomes of different organisms and see which parts of DNA are conserved or more specifically which aminoacids are conserved in proteins.

 

[Mentat]

Useful DNA stays intact simply because if it didn't, the organism would die (or at least have a survival disadvantage).

It's called DNA conservation, you can compare genomes of different organisms and see which parts of DNA are conserved or more specifically which aminoacids are conserved in proteins.

So, there are specific processes which work to make DNA very resilient, and these continue after the being has died?

 

[PhilipF]

I was surprised to hear about surviving fossil dna as I thought that in a fossil all the organic material was replaced by minerals . However I found this site which seems reliable :
http://scienceworks.museum.vic.gov.au/pdf/TerrorsaurusKit1.pdf
However it does state that the dna recovered was mitochondrial and therefore could not be used to reconstruct dinosaurs .

 

[DocToxyn]

So, there are specific processes which work to make DNA very resilient, and these continue after the being has died?

The conservation of DNA, brought up by Moninque, along the timelines that you are interested in is more a "conservation of code" and not an actual "conservation of substance". Thus particularly useful sequences of DNA which code for particularly useful proteins are passed along from generation to generation and species to species (usually not directly, but during the divergence of one species from another) and the DNA is conserved across time. Terms like consensus sequences and homology between species get tossed around when you begin to discuss how similar or how different specific DNA or protein structure is between organisms.

I think another way of getting at what you are asking is if I were to drop dead today, how long would my own DNA be viable for my "reconstruction" (assuming all other technological variables are covered). I would imagine much has to do with how I died and how well preserved I am, i.e. frozen, sealed in amber, etc. Even under optimal conditions, I don't imagine enough intact DNA would remain for long, but I don't have any exact predictions...anyone?

 

[Monique]

Oh, you're talking about actual fossil DNA exposed to the environment? I actually don't know how fast DNA degrades, it would depend on the conditions under which it has been. You might find an answer in forensic biology, where they use DNA from extreme conditions to identify people.

 

[flatmaster]

Looking back to the original question of some DNA preserved in Amber or whatnot. I couldn't tell you how long it would take to degrade, but I'm rather confident it would degrade with a half life. Consider a radioactive isotope. Any given nucleus has the same probability of decaying. Mathematically, this leads to expenontial decay with some halflife. I ASSUME, once a DNA sample is already preserved, any given chemical bond within the DNA has equal probability of being struck by ionizing radiation and degrading. This again would lead to a half-life for the amount of genetic material remaining. Anyone agree?