The Cattle Gene Map.

Cave paintings in Europe and North Africa depict wild cattle, the aurochs (Bos primigenius), among the prized prey of Stone Age hunters. These majestic animals stood nearly 2 M at the withers and had horns up to 1 M long. Bulls are usually shown as dark brown or black with cows and calves reddish brown, although white and speckled animals also appear in the paintings (Felius 1985). The aurochs spread out of western Asia after the Ice Age (250,000 yr ago) and are believed to have survived in Europe until early in the 17th century. Sometime before their extinction, probably 7000 to 10,000 yr ago, aurochs were domesticated. At least 2 domestications are likely represented in breeds of cattle at the time of this writing. Bos primigenius primigenius, a European auroch subtype evidenced by the fossil record, is thought to be the ancestor to today's humpless breeds of cattle given the species designation Bos taurus. An Asian auroch subtype, Bos primigenius namadicus, probably gave rise to today's humped zebu breeds classified as Bos indicus. Although domestic breeds of cattle are divided into 2 species, they are totally interfertile; in fact, several synthetic breeds have arisen in this century from intercrosses of taurus and indicus breeds. Chromosome numbers are identical: 29 autosomes, all of which are acrocentric, and a submetacentric X. Morphology of the Y chromosomes is the only recognized structural difference in B. taurus and B. indicus karyotypes. Thus, the "cattle" gene map developed to date and discussed in this article is for 2 species that many people, including myself, believe should be reclassified as 1. Cattle are members of the subfamily Bovinae, the family Bovidae, the suborder Ruminantia, and the order Artiodactyla. A standard karyotype for cattle was resolved by Popescu and others (1996), with gene nomenclature following the guidelines for human gene nomenclature as recommended by the International Society for Animal Genetics (ISAG). Loci without human equivalents are named according to the recommendations of the Committee on Genetic Nomenclature of Sheep and Goats (COGNOSAG 1995).