On Headspot (to German "head spot") is a white mark on the forehead. The shape can vary. On Headspot usually occurs along with other white markings. It is possible in all colors, but is not visible on light colors may.
The standard of the rat with Head Spot
There a Headspot always occurs in conjunction with a drawing, there is in the American Fancy Rat and Mouse Association (AFRMA) and the National Fancy Rat Society (NFRS) no separate standard for a Headspot. are in the AFRMA Headspots approved in conjunction with the drawing Variegated and Roan, at Essex is a Headspot required. The Headspot should be on the front, centrally positioned, round or oval and no larger than the eye of the rat. The NFRS permits Headspot at Variegated and chinchilla and writes him at Essex.
The Genetics of Head Spots
In many cases, there is an indication, that Headspots always occur together with drawing alleles of the locus Hooded H, as self-rats show Headspots demonstrate. This would indicate, that it is at or Head spot to an allele at the H locus that a genetic coupling with alleles at the H locus is present. Robinson (19981)Robinson, R. (1998), Headspot and Dilute Mutation in the Norway Rat, The Journal of Heredity 89(1), 100-101) could show, that neither is the case. In a stock of agouti rat wild origin animals were treated with Headspots found. Matings of Agouti Head Spot x Agouti resulted in F1 only agouti animals, fell in the F2 40 Agoutis, 11 agoutis with Headspots, 9 Blacks und 4 Blacks mit Headspot. This points to a simple recessive allele. Investigations regarding a possible Allelismus of Headspots show to Hooded, that this is from Head Spot to its own locus, which is abbreviated hs. Linkage studies suggest, that this locus is not associated with the locus Hooded. It was noticeable, that all F2 rats had a white belly patch, as otherwise only by the alleles h(i) and h caused the Hooded-locus. But as the Headspot-Lokus is not connected to the Hooded-locus, the abdominal patch in a different way must arise. Robinson (19982)Robinson, R. (1998), Headspot and Dilute Mutation in the Norway Rat, The Journal of Heredity 89(1), 100-101) According to the stain is independent of the Hooded allele and is a consequence of incomplete migration of neural tube from the melanoblast. The presence of h(i)-Allele increases the spot, the presence of the h allele results, that the stomach is almost completely white. the locus, on which the spot is encoded Head, located on chromosome 15 on position 84.6-91.2 MB, the relevant candidate gene is the endothelin receptor type B gene EDNRB (Kuramoto et al. 20103)Kuramoto T1, Yokoe M, Yagasaki K, Kawaguchi T, The mafuji K, Serikawa T. (2010), Genetic analyses of fancy rat-derived mutations, Exp Anim. 2010;59(2):147-55). Robinson (19984)Robinson, R. (1998), Headspot and Dilute Mutation in the Norway Rat, The Journal of Heredity 89(1), 100-101) succeeded also, to achieve Blessen through specific selection in the direction of greater Head spots in the form of an inverted V-. Often these blazes were drawn irregularly. This know out, that the Head Spot allele also in the form of a recessive blaze (in contrast to the dominant white spotting blaze) may be.
References [ + ]
|1, 2, 4.||↑||Robinson, R. (1998), Headspot and Dilute Mutation in the Norway Rat, The Journal of Heredity 89(1), 100-101|
|3.||↑||Kuramoto T1, Yokoe M, Yagasaki K, Kawaguchi T, The mafuji K, Serikawa T. (2010), Genetic analyses of fancy rat-derived mutations, Exp Anim. 2010;59(2):147-55|