March 8, 2007 — Tyrannosaurus rex may have been over 43 feet long, but the meat-loving predator and several other large dinosaurs had relatively little DNA in their cells, according to new research.
The study, published in this week's Nature, is the first to estimate dinosaur genome size. A genome is an organism's complete set of genetic information, which includes DNA and RNA.
Since prior research by the same team demonstrated that small genomes correlate with high metabolism, the findings suggest T. rex, Allosaurus, Deinonychus (aka "Terrible Claw") and certain other large carnivorous dinosaurs may have been very active, fast moving animals, as many popular films, such as "Jurassic Park," portray.
"There is a widely held idea that metabolic rate...may limit genome size, since maintaining a high metabolism would be most effective with smaller cell sizes," explained Andrew Shedlock, who worked on the study.
Shedlock, a research associate in the Department of Organismic and Evolutionary Biology at Harvard, and colleagues first studied birds and reptiles living today.
Their findings suggested that bone cell size in vertebrates is linked to genome size. The smaller the bone cells, they found, the smaller the genome.
The specific cells they studied are found in durable, protected pockets found in bone tissue. By measuring the size of those pockets in 31 extinct birds and dinosaurs, the scientists were able to estimate genome sizes in those species as well.
In addition to the findings about carnivorous dinosaurs, the researchers discovered certain plant-eating dinos, like Protoceratops and Psittacosaurus, also possessed genomes that were smaller than those of other dinosaurs and most other vertebrates — living or extinct.
The genetic "downsizing" appears to be due to fewer repetitive elements and less non-coding DNA.
"Aside from higher metabolic rates, smaller genomes have been correlated to longevity and faster rates of development," Edwards told Discovery News.
That suggests certain dinosaurs grew up fast, lived fast and yet might have been relatively long-lived.
