What is ancient DNA and how is it extracted from fossils?

Also, if fossils are just mineralised bones, how could it still contain organic material in them? How could DNA be extracted from these fossils?



ThanksWhat is ancient DNA and how is it extracted from fossils?
Ancient DNA is DNA that is extracted from the remains of organisms that have been dead for a long time, but not necessarily fossilised.

In fact, the source material of most ancient DNA studies is not fossils, but specimens collected only a few decades or centuries ago. For example, a collection of old hunting trophies can be used to compare the genetic diversity of an ancient population of animals to that of its modern descendants.

As you pointed out in your question, during fossilisation, all the organic material is replaced by minerals. But fossilisation is a gradual process and some of the DNA can be preserved, in ideal conditions, for tens and possibly hundreds of thousands of years.

Anyway, even in the best possible conditions, DNA is subject to progressive degradation by biological, chemical and physical agents. One million years is the theoretical upper limit to the age of fossil DNA but, in practical terms, only fossils aged no more than a few tens of thousands of years have been successfully used. Studies that claimed to have retrieved DNA sequences from fossils many million years old have been subsequently proven to be the result of sample contamination (and Jurassic Park is just science fiction ;-).

As for the extraction method, the precise protocols to be used are modified according to the nature of the specimen but, in general, it's not so different from that used for recent specimens.

A small fragment is cut out of the specimen, ground to a fine powder and suspended in an extraction buffer where the DNA contained in the sample is solubilised. The solution, now containing the DNA, can be treated with different methods to remove other unwanted substances. Finally the DNA in the solution is concentrated either by precipitation or by adsorption on a silica matrix.What is ancient DNA and how is it extracted from fossils?
Usually, in most cases, DNA disappears after that long period of time. However, occasionally, DNA somehow survived through the classes and dirt and water. This is exceptionally rare.What is ancient DNA and how is it extracted from fossils?
Fossils don't have DNA. Anyone who claims otherwise is wrong. As has already been repeatedly explained to you.

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