Twilight is a Thoroughbred mare bred and raised at the McConnville Barn at Cornell University. She provided the DNA for the whole genome sequence of the horse that was completed and assembled at the Broad Institute in Cambridge, MA. The Thoroughbred originated in England during the late 1600s as a race horse. One of the oldest stud books was established to maintain records and aid breeders in selecting for sound, fast race horses. Thoroughbred racing was popular and was adopted worldwide over the next 3 centuries. All modern Thoroughbred horses trace 81% of their genes to 31 ancestors.
Bravo is a male Thoroughbred, closely related to Twilight. He lives at the McConnville Barn at Cornell University with Twilight. DNA from his blood cells was cut into large fragments and cloned into a tool called a bacterial artificial chromosome (BAC). The collect of clones is called a “BAC Library”. Scientists can use BAC libraries to find and study DNA sequences. Scientists use the information from Bravo's DNA together with Twilight's whole genome sequence to better understand the interplay of genetics, health and performance in horses.
Desert Heir (better known as Bissy) was a male American Saddlebred horse. His blood cells grow very well in cell culture and it was easy for cytogeneticists to study his chromosomes. When it was time to determine the order of genes on a chromosome, the results from computer assembly of Twilight’s DNA sequences were double checked by mapping the BACs for some genes to Bisquette’s chromosomes. Sadly, he passed away due to natural causes at the age of 26 in May 2015. American Saddlebreds were developed in the southern United States during the late 1800s. They were prized for their smooth gaits, good disposition and intelligence. Many of the famous television horses of the 1960s were Saddlebreds, including Mr. Ed and Fury!