- "Paleo-DNA? From what source? Where do you get 100 million year old dinosaur blood?!"
To create dinosaurs you need a blueprint of the animals. From the many skeletons that have been discovered we can have a reasonable picture of what the animals looked like; but that isn't enough to rebuild the animals. We need know the genetic code of dinosaur DNA in order to grow them.
Fossils can contain proteins. From the protein code, the corresponding genes can deduced. However, of an animals total genome only 1% consists of genes. Therefore, another DNA source is needed.
In the movie Mr. DNA explains how dinosaur DNA can be found:
"A hundred million years ago, there were mosquitoes, just like today. And, just like today, they fed on the blood of animals. Even dinosaurs! Sometimes, after biting a dinosaur, the mosquito would land on a branch of a tree, and get stuck in the sap! After a long time, the tree sap would get hard and become fossilized, just like a dinosaur bone, preserving the mosquito inside!"
Preservation characteristics amber Edit
Amber is a unique preservational mode.
Dinosaur cells Edit
In all Jurassic Park media dinosaur DNA is found in yellow amber. This can only be done if dinosaur cells would be present in amber. In the novels and films dinosaur cells are present inside mosquitoes that had just fed on dinosaurs. An alternative suggestion is that dinosaur tissue could have ended up in amber.
Blood-sucking insects Edit
In the Jurassic and Cretaceous Periods the existed insects that fed on dinosaurs. The theory is that if such an insects got stuck in amber, the dinosaur blood was preserved. Blood contains red and white blood cells, which contain nuclei with DNA.
The mosquito had to have had just one species of dinosaur as its food source to avoid a mix-up. Since some species of mosquito have a female lifespan of only a few days and tend to lay eggs following each feeding, this is semi-plausible, though in that case dozens of mosquitoes of different species would have to be found in order to recreate as many kinds of dinosaurs.
Scientists DeSalle and Lindley criticised this idea. According to them the cells and DNA are broken down by nucleases in the mosquito gut before the amber stops all cellular processes in the insect. Bacteria in the insect's gut would break down the DNA. Many insects extracted from amber have been found to be completely hollow. In 2004 the Poinars published that they had discovered intact nucleated blood cells from reptiles in the gut of a Sandfly encased in Cretaceous amber.. This proves that dinosaur cells can survive in an insect's gut.
Dinosaur tissue Edit
DeSalle and Lindley proposed the idea that dinosaur tissue could end up in amber without the need of insects. Imagine that a tree fell on top of a dinosaur. In a fight a dinosaur is pushed against a tree. In a fight pieces of dinosaur are raining against a tree. A scavenger is ripping flesh out of a carcass and the pieces are flying around. A small dino tries to flee into a tree and is wounded by a branch.
Reptilian tissue from the Mesozoic Era has been found in amber. In 2002 skin fragments of a Baabdasaurus lizard was discovered in 120 million year old Lebanese amber. In 2005, fragments of reptile skin were found in Cretaceous amber from France .
DNA recovered from amber Edit
Whether DNA can survive 65 million years in amber is a matter of scientific debate. It was long believed that in ideal conditions (like permafrost) DNA could only survive for a million years. This dogma wasn't challenged by experimental evidence until the research of Allentoft in 2012,
In 1992 DeSalle (who later wrote The Science of Jurassic Park) and his team reported that they had extracted and sequenced DNA from a termite (Mastotermes electrodominicus) entombed in 25-30 million year old amber.
The first discovery of Mesozoic DNA was claimed by Cano and his team (see video). They claimed that they had extracted and sequenced two DNA fragments from a 120-135-million-year-old weevil (Lebanorhinus succinus). One fragment (315 nucleotides long) coded for part of ribosome RNA. The other fragment (226 nucleotides) coded for a piece non-functional RNA.
Many scientists have criticised these discoveries. Many scientists were unable to extract DNA from comparable samples. Some have claimed the DNA was the result of contamination. Scientists Gutierrez and Marın showed in 1998 that the latter Cretaceous Weevil sequence showed more resemblance with DNA from the fungus Pichia guilliermondii (known to them as Candida guilliermondii) than insects.
The scene featuring a close-up of the mosquito clearly shows fuzzy antennae, meaning the particular insect is male. This was likely for a cinematic effect, as only female mosquitoes suck blood.
- ↑ Poinar G. and Poinar R. (2004). Evidence of vector-borne disease of Early Cretaceous reptiles, VECTOR-BORNE AND ZOONOTIC DISEASES, Volume 4, page 281-284. PMID 17710310.
- ↑ Arnold E.N., Azar D., Ineich I. and Nel A. (2002). The oldest reptile in amber: a 120 million year old lizard from Lebanon, J. Zool., Lond., Volume 258, page 7-10. Link
- ↑ Perrichot and team (2005). Reptile skin remains in the Cretaceous amber of France
- ↑ Perrichot V., Marion L., Neraudeau D., Vullo R., Tafforeau P. (2008). The early evolution of feathers: fossil evidence from Cretaceous amber of France, Proc. R. Soc. B, Volume 275, pages 1197–1202.
- ↑ McKellar R.C., Chatterton B.D.E., Wolfe A.P., Currie P.J. (2011). A Diverse Assemblage of Late Cretaceous Dinosaur and Bird Feathers from Canadian Amber, Science, Volume 333, pages 1619-1622.
- ↑ Allentoft M.E., Collins M., Harker D., Haile J., Oskam C.L., Hale M.L., Campos P.F., Samaniego J.A., Gilbert M.T.P., Willerslev E., Zhang G., Scofield R.P., Holdaway R.N., Bunce1 M. (2012) The half-life of DNA in bone: measuring decay kinetics in 158 dated fossils, Proceedings of the Royal Society Biological Sciences, Volume 279, page 4724-4733.
- ↑ DeSalle R., Gatesy J., Wheeler W., Grimaldi D., (1992) DNA Sequences from a Fossil Termite in Oligo-Miocene Amber and Their Phylogenetic Implications, Science, Volume 257, page 1933-1936. Link
- ↑ Cano R.J., Poinar H.N., Pieniazek N.J., Acra A., Poinar G.O. Jr. (1993) Amplification and sequencing of DNA from a 120-135-million-year-old weevil. Nature, Volume 363(6429), page 536-8.
- ↑ DNA sequence L08072 on GenBank.
- ↑ Never included on GenBank. Sequence is shown here: Cano ITS sequence
- ↑ Hebsgaard M.B., Phillips M.J., Willerslev E. (2005) Geologically ancient DNA: fact or artefact?, TRENDS in Microbiology, Volume 13(5), page 212-220. Link
- ↑ Gutierrez G., Marın A., (1998) The Most Ancient DNA Recovered from an Amber-Preserved Specimen May Not Be as Ancient as It Seems. Mol. Biol. Evol., Volume 15(7), page 926–929. Link