Modern genetic research often works with what are known as reference genomes. Such a genome comprises data from DNA sequences that scientists have assembled as a representative example of the genetic makeup of a species.
To create the reference genome, researchers generally use DNA sequences from a single or a few individuals, which can poorly represent the complete genomic diversity of individuals or sub-populations. The result is that a reference does not always correspond exactly to the set of genes of a specific individual.
Until a few years ago, it was very laborious, expensive and time-consuming to generate such reference genomes. For this reason, researchers concentrated on human genomes and the most important biological model organisms, such as the roundworm C. elegans.
However, as researchers now have access to fast sequencing machines, sophisticated algorithms that assemble DNA sequence readouts into complete chromosomes, and much greater computing power, creating reference genomes for other species has become increasingly practical. If researchers are to better understand evolution and other fundamental questions of biology, they need high-quality reference genomes for as many species as possible.
This includes livestock. For domestic cattle (Bos taurus), only a single reference genome was available until recently: from a Hereford cow called Dominette. Researchers had previously compared other DNA sequences of cattle against this reference to detect genetic variations and define corresponding genotypes. However, as it did not contain any genetic variants by which individuals differ, the previous reference did not reflect the diversity of the species.
Gap filled
A research team led by Hubert Pausch, Assistant Professor of Animal Genomics at ETH Zurich, has now filled this gap: with the genomes of three further breeds of domestic cattle, including the Brown Swiss (Original Schweizer Braunvieh), two closely related (sub-)species such as the zebu and the yak, and the existing reference genome for domestic cattle, the researchers have created a “pangenome”. The study detailing these findings has just been published in the scientific journal PNAS.
