Science - February 14, 2012

Unique DNA mutation in rare cow

Witrik cattle have an unusual genetic structure never before observed in mammals. Pieces of DNA form a circle and move from one chromosome to another.

This is reported by Belgium researchers from Liège and the Centre for Genetic Resources, the Netherlands (CGN) in Wageningen in early February in Nature. CGN collected DNA from Witrik cows jointly with other Belgium researchers and the Dutch Rare Domestic Animal Breeds Foundation. These animals are characterized by a white stripe on their backs. The native Witrik is still being bred by several Dutch breeders to maintain its numbers. The Belgian Blue from Belgium also has this distinctive colour marking.
Liège researchers examined the DNA of these breeds for a genetic explanation of the white stripe. They discovered that a piece of DNA of chromosome 6 forms a circle which then moves to chromosome 29. When this circle is present in a chromosome 29, the white stripe appears in the Belgian Blue and the coloured Dutch animals. If both chromosomes 29 have the circle in them, the animal is almost entirely white.
Never before have geneticists shown that DNA pieces can move from one to another chromosome in the form of a circle. This discovery puts the researchers on a new trail in the study into mutations in hereditary material. Nothing much changes for the Witrik cattle breeders, though.

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