In 1925, a sled dog named Balto helped carry life-saving medicine through blizzards. A new DNA study reveals what made him so tough.

New York's Central Park has a statue dedicated to him, and there's even been a movie about him: a sled dog named Balto. Now he is the focus of a DNA study, 90 years after he died, to see what made the canine so famously tough.

In 1925, this Siberian husky was part of an expedition in Alaska called the serum run, the goal of which was to bring life-saving medicine to young people in the remote town of Nome that were threatened by diphtheria.

The mission in horrendous blizzards conditions involved a series of sled dog teams transporting the anti-toxin relay-style from the city of Anchorage -- a more than 600-mile-long trek.