Bull Dog and his brother Sir Gallahad III as leadingsires provided that all US racehorses became strongly inbred. The major historic event was bringing Sir Gallahad to the US. He stood 2 seasons in France before being purchased by an American syndicate headed by A. B. Hancock and was relocated to Claiborne Farm in Kentucky. His first American crop included Triple Crown winner Gallant Fox. for Woodward. He became the American leading sire in 1930, 33, 34 & 40 and was of course also a leading broodmare sire.

We can freely believe that all these hundreds of runners are essentially copies !

The horse genome has 64 pairs of diploid chromosomes and contains about the same amount of DNA as the human genome (3 billion base pairs). Horse chromosomes 22, is nearly identical to human chromosome 20 and part of mouse chromosome 2. These 3 regions not only share most of the same genes, but the genes also appear in the same order in these 3 species. See Genome mapping in the horse by Gabriella Lindgren, Uppsala.

The X chromosome is similar in terms of the order of nucleotides in horses and humans. Horse chromosome 11 matches human 17. Coatcolor patterns and very many other traits are given in the book by Bowling & Ruvinsky.