The work has involved several hundred researchers all over the world and is being reported in three articles in Nature. The publication is being coordinated with Genome Research, which is presenting the findings in a thematic issue the same day.
The main article presents the entire genetic make-up of the hen for the first time. The scientists have mapped the consequences of all of the building blocks of the DNA of the hen. This is the first bird and the first domesticated animal to have its DNA charted. Previously scientists have mapped the genetic make-up of the human being, the rat, and the mouse.
The results show that birds have roughly the same number of genes as humans, about 20,000, but they are found in only one third the amount of DNA. This is because birds lack much of the junk DNA that humans have. Moreover, the mapping shows that the genetic make-up of birds is stable and very similar across many species, whereas that of mammals is often rearranged.
“It is a major scientific event when the genes of an organism are charted, and as a Swedish scientist it is of course tremendous to be part of such a huge international project. What’s more, this means that we have a good chance of being able to continue to pursue cutting-edge research, since we use birds as organisms under study in our evolutionary research,” says Professor Hans Ellegren.
The mapping of the genes of the hen was performed on a red jungle hen, the wild ancestor of our domesticated hen. In one part of the study the scientists even found how the genes differ among three different races of domesticated hens: a laying hen, a broiler, and a silkie. The laying hen used in the project comes from a line of white leghorns developed at SLU in Uppsala.
The results of the comparison demonstrate that the domesticated hen is far from inbred and as a matter of fact evinces greater genetic variation than humans. This means that the average size of the population of red jungle hens must have been considerably greater than for human beings over the last million years. What’s more the study shows that the domestication of the hen, which took place about 7,000 years ago, must have involved a large number of individuals, since such extensive genetic variation has been retained in the domestic hen.
“The findings now being presented will be of great significance for the further genetic study of our domesticated hens. It will be much easier to identify genes that determine various characteristics,” says Professor Leif Andersson.
The three Swedish research teams that participated in the study have been directed by Hans Ellegren at the Department of Evolution, Genomics, and Systematics at Uppsala University, Leif Andersson at the Department of Medical Biochemistry and Microbiology at Uppsala University and the Department of Domestic Animal Genetics at SLU, and Björn Andersson at the Center for Genomics and Bioinformatics at the Karolinska Institute.
Caption to the attached image: The laying hen Agda, used in the comparative study of the genetic make-up of the domestic hen, comes from a line of white leghorns developed at SLU in Uppsala. Photo: Ulrika Gunnarsson