Molecular characterization using DNA markersDNA studies shed light on relationships and diversity among animal breeds. The extent and nature of genetic diversity of Nordic and Baltic farm animals has been investigated by typing DNA markers in a set of individuals belonging to several breeds. To date, cattle, sheep, horse and poultry breeds have been studied and research on goat breeds was initiated in 2011. The most useful markers for these studies have been microsatellites, from sire to son inherited Y-chromosome’s markers and from dam to daughter and son inherited mitochondrial DNA. In addition, the structure and action of important genes have been analyzed. Diverse set of DNA markers A microsatellite is short sequence of DNA, consisting of a unit of 1 to 6 base pairs (bp, a unit of DNA) that is repeated sequentially 10 – 100 times along the DNA molecule. For example, the repeat unit TG (thymine-guanine) is very common in cattle. Different individuals and different breeds may have varying numbers of repeat units of the same microsatellites. Such differences in numbers of repeats represent the core information used in making inferences on genetic diversity.
Single nucleotide substitutions and microsatellites have been investigated on the Y-chromosomes of some domestic animal breeds, which allows investigation of the paternal history of those populations. DNA marker data provide information on livestock diversity and history DNA marker data provide useful information on the origins, relationships, genetic diversity and genepool development of domestic animal breeds. The data help to identify those breeds that are genetically distinct. Genetically differentiated breeds can carry genes and gene combinations of economic and scientific importance and which determine an animal's capacity to adapt to particular environments. The genetic diversity of such important breeds should be conserved in ex situ and in situ . Knowledge on the relationships within and among populations can also be used in the management of endangered farm animal breeds. Frozen sperm and embryos representing the genetic diversity of endangered breeds can be used to conserve a breed, particularly if it is threatened by a high rate of inbreeding. Using DNA data, it is possible to get information on the history of species and distinct breeds within a species even when the original domestication events occurred thousands of years ago. Using techniques based on molecular biology it has been possible to determine the number of separate domestication events that occurred and the numbers of individual wild ancestral populations from which a specific domestic breed descended. For example, the sheep appears to have descended from five separate Asiatic Mouflon populations, and the horse too developed through several separate domestication events. Over recent years the laboratory equipment and techniques used to investigate the genomes of farm animal species have developed very rapidly. It is now possible to analyze simultaneously hundreds of thousands of DNA markers (using so-termed SNP Microchip technique; SNP, Single Nucleotide Polymorphism), and to sequence DNA of the whole genome of an individual. Using this genomic information, key genes can be located and characterized that affect an animal's distinct traits such as productive yield, growth, disease resistance and fertility. These new methods will provide critical information on animal genetic resources and on the importance of the various breeds for the maintenance of species-level biodiversity. Responsible: Anne Præbel
Icelandic leader sheep (photo: Jón EirÃksson) are relatively close relatives to other primitive breeds such as Old Norse sheep often called Wild sheep (see photo below, photo: Hilde Buer).
The commercially bred breeds such as Norwegian White Sheep, see below, are crossbred with international breeds for better meat production (photo: The Norwegian Association for Sheep and Goat Breeders).
|
