A team based at Kent University's School of Biosciences analysed the genomes of modern-day species, including a chicken, a zebra finch and a budgerigar.
A genome is full the set of genetic material inside a cell, and it contains all the information needed to build and maintain an organism, whether it is a fish, plant, human or dinosaur.
By comparing the chromosomes of turtles and birds (the living descendants of dinosaurs), the team worked out the likely genome of a common ancestor of those animals. It lived 260 million years ago (about 20 million years before dinosaurs first emerged).
They then traced how chromosomes changed over evolutionary time from the common ancestor of turtles and birds to the present day.
The results suggest that, had scientists had the opportunity to make a chromosome preparation from a theropod dinosaur like a T. rex, it might have looked very similar to that of a modern-day ostrich, duck or chicken.
Prof Paul Barrett, a Museum dinosaur expert, contributed to the study.
He says, 'Using these advanced genomic techniques we can reconstruct a plan for how the dinosaur genome was organised, shedding further, more detailed light on the biology of these amazing animals.
'Although this won’t allow us to resurrect a Diplodocus, or any other extinct dinosaur, it does show how many features that used to be considered unique to birds appeared much earlier in time, in their theropod ancestors, including at the genome level.'
Scientists don't have access to DNA from any extinct dinosaurs, but they can study that of living dinosaurs (birds) and their other more distant living relatives.
Prof Darren Griffin, an expert on chromosomes at Kent's School of Biosciences, says, 'DNA is pretty stable but the longest you would expect it to last, even in the best of conditions, would be about a million years. T. rex hasn’t been seen wandering the earth for at least 66 million years.
'Even if you could get intact dino DNA then to recreate the precise conditions both in the cell, and in the egg, to generate an embryo of an animal that became extinct tens of million years ago would be next to impossible.
'In Kent and at the Royal Veterinary College, we used a combination of lab-based techniques and computer wizardry. We selected the genomes of certain birds, turtles and lizards and essentially did a triangulation exercise to infer the structure of long dead species.'
How is a turtle like a dinosaur?
Scientists now agree that birds alive today are living dinosaurs, directly descended from theropods (carnivorous dinosaurs that walked on two legs).
Birds have a lot of chromosomes compared to most other species and this is possibly one of the reasons why they are so diverse. This research suggests that the pattern of chromosomes seen in early dinosaurs, and the later theropods, is similar to that of most birds.
We also know that turtles, crocodiles and birds also share a common reptile ancestor. Turtles diverged from archosaurs (birds and crocodiles) about 255 million years ago.
Prof Barrett explains, 'Turtles aren’t closely related to dinosaurs, but they are one of the living groups of reptiles that can be used to study the relationships of dinosaurs and some of the features that they would have possessed.
'Birds are living dinosaurs, and crocodiles are their next nearest relatives, followed by turtles, lizards and snakes.'
Dr Becky O'Connor, senior postdoctoral researcher and co-author of the paper, says, 'The technique used in this study allowed us to determine the genome structure of the turtle-bird ancestor.
'Turtles are one of the very few species that have similar looking chromosomes to birds. Until now, the tools required to compare their chromosomes were not available. In our study, we added fluorescent labels, called "DNA probes", to the chromosomes of birds and turtles so that we could locate the stretches of DNA that match in the two species.
'The process then involved tracing the changes that occurred from the bird-turtle ancestor. The evolutionary path examined the point when dinosaurs first emerged, through the theropod dinosaur line, and beyond several mass extinction events, including the most recent one 66 million years ago.'