There are still stretches missing, but the researchers estimate that the genome is roughly 80% complete. The work could provide insights into the extinction of the mammoth and also resurrects questions about the viability of cloning long-dead species. ... But most scientists are doubtful this could ever be achieved. The changes that occur to an animal's genetic sequence after its death poses one of the principal hurdles. "It's a bit like trying to build a car with only 80% of the parts and knowing that some of the parts are already broken," said Jeremy Austin, deputy director of the Australian Centre for Ancient DNA at the University of Adelaide. "Even if we did have the genome in its entirety, we still have the problem of knowing what is a real mutation versus what is (a) sequencing error or DNA damage. At a genome scale, this in itself is an almost insurmountable problem. "After this we have the issues of how to construct artificial chromosomes."