Though placid enough to be managed by humans, yaks are robust enough to survive at 4,000 meters (~13,000 feet) altitude. Genomic analyses by researchers of Ludwig-Maximilians-Universitaet (LMU) in Munich, Germany show that yak domestication began several millennia ago and was promoted by repeated crosses with cattle. The first systematic genome-wide comparison of the genetic heritage of yaks and cattle shows that about 1.5% of the genome of Mongolian yaks is derived from domesticated cattle. While male hybrids are sterile, hybrid females can be backcrossed to male yaks for several generations, which allows for the stable introgression of short regions of bovine chromosomes into the yak genome. The results of the new study suggest that yak hybridization began thousands of years ago. Dr. Ivica Medugorac, who heads a research group in population genomics as the Chair of Animal Genetics and Husbandry at LMU, is the first and corresponding author on the new paper, which was published online on January 30, 2017 in Nature Genetics. "Our results indicate that hybridization between yaks and cattle began more than 1,500 years ago, and has continued with varying intensity ever since," Dr. Medugorac says, and points out that written records also testify to early hybridization of yaks by Mongolian breeders. The Nature Genetics article is titled “Whole-Genome Analysis of Introgressive Hybridization and Characterization of the Bovine Legacy of Mongolian Yaks.” In collaboration with Dr. Aurélien Capitan of the Université Paris-Saclay, Dr. Stefan Krebs of the Laboratory for Functional Genome Analysis at LMU's Gene Center, and colleagues from other European, American, and Mongolian institutions, Dr. Medugorac has mapped the distribution of cattle genes in the yak genome.
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