Better Burgers through DNA?

Nearly six years ago, an unassuming Hereford named Dominette 01449 took the first steps toward bovine history, by donating her DNA to science. Dominette’s genome sequence was published today in the journal Science, the first livestock mammal to have its genome sequenced and analyzed. Scientists say the research will lead to better beef and dairy products and will shed light on mammalian evolution and the human genome.

According to a statement from the National Human Genome Research Institute, the analysis revealed:

The genome of the domestic cattle (Bos taurus) contains approximately 22,000 genes and shares about 80 percent of its genes with humans. The researchers also report that the organization of human chromosomes is closer to that of domestic cattle than to those of rats or mice.

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Segmental duplications in the domestic cattle genome have also resulted in specialized roles for genes involved in immune response, such as those that make antimicrobial proteins in milk and their intestines. Researchers think these genes developed over time in response to the diversity of microbes that domestic cattle encounter and the vulnerability of animals that live in large herds to the spread of infectious diseases.

Researchers also compared the genome sequence to that of other kinds of cattle, including the Holstein, Angus, Jersey, Limousin, Norwegian Red and Brahman. The findings shed light on the genetics of domestication and show that domestic cattle may have a troubling lack of genetic diversity.

According to GenomeWeb,

The team identified specific regions of the genome associated with traits such as milk yield, meat quality, and disease or pest resistance – traits that have been selected through cattle breeding programs. But, they warned, the HapMap data reveals evidence of bottlenecks in cattle populations following domestication.

“The bovine HapMap data show that cattle have undergone a rapid recent decrease in effective population size from a very large ancestral population, possibly due to bottlenecks associated with domestication, selection, and breed formation,” University of Missouri researcher Jerry Taylor, who was part of the Bovine HapMap team, said in a statement. “The recent decline in diversity is sufficiently rapid that loss of diversity should be of concern to animal breeders.”

University of Illinois at Urbana-Champaign Institute for Genomic Biology Director Harris Lewin, who led two teams involved in cattle genome sequencing, echoed this sentiment in a perspectives article appearing in the same issue of Science. Lewin noted that the apparent links between animal breeding and genomic architecture suggest that “genetic diversity should be carefully monitored as genomic selection for quantitative traits takes its place as a routine technology for animal genetic improvement.”

“Comparisons of the cattle genome to that of other mammals [were] … expected to yield exciting new information on how mammalian genomes evolve, mechanisms of gene regulation, genetic control of complex traits, and host-microbe interactions,” Lewin wrote. “The cows have not disappointed us.”