Emmeline Hill, a 35-year-old geneticist at University College Dublin, has horseracing in her blood. For generations, her family has bred thoroughbreds on their farm in County Wexford, in southeast Ireland. Her grandmother, Charmian Hill, owned Dawn Run, probably the most successful race mare in the history of steeplechase or National Hunt racing.

Considering her own breeding, it seems only fitting that Emmeline is now building a research program to answer an age-old question: What makes a good racehorse?

"Everyone knows that some horses run faster than others, and most people want to know which ones. But I want to understand why," she says. "I've always been interested in horses and in science, and I always knew I was going to be a scientist. It seemed natural to bring them together, and in a way that hasn't really been done before."

Thoroughbreds are natural athletes, selected over 400 years for speed and stamina. Over that time, they have developed several extreme and unique physiological characteristics, Hill says. Those traits include an unusually large muscle mass, massive capacity for aerobic exercise relative to their body mass, as well as a very high anaerobic capacity. In addition, they have an adaptation that may be unique to thoroughbreds: the ability to contract the spleen to release more red blood cells and improve the blood oxygen-carrying capacity - "Something human athletes would love to be able to do," she notes.

Hill is using sequence analysis and other genomic techniques to compare gene-expression profiles from horses exercising and at rest, and from thoroughbreds and non-thoroughbreds. As well as shedding light on what makes an elite racer, the results could be helpful in human physiology, athletic performance, and even obesity and exercise. The results might also be used one day by thoroughbred breeders and trainers. The industry is often seen as conservative, but Hill says successful breeders and trainers are always keen to embrace new ideas.

Hill's funding from Science Foundation Ireland - up to €1.2 million ($2 million US) over five years - is one of a small number of President of Ireland grants specifically given to young researchers to kick-start their careers. Her team of three PhD students and one postdoc is part of a small but growing community of equine geneticists worldwide.

With the horse genome having been successfully sequenced in April 2007, Hill expects research activity to take off. University of Kentucky's Ernie Bailey who helped coordinate the international equine gene mapping effort, echoes that view. "The work is well supported by Science Foundation Ireland and employs cutting-edge technologies. Dr Hill and her students will provide valuable information for breeders to use in crafting better racehorses."

Hill, who was part of the genome sequence consortium, has a number of research papers in preparation, but she won't divulge her findings just yet. As for whether she plans to follow her grandmother's footsteps and become a horse breeder, Hill responds with a quick, good-humored "No!"

"Although, if I had the money," she says, "I might consider owning a racehorse. Especially one with favorable genes."