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Frosty - lessons from crosses

Frosty as a sex-linked factor with no effect on the coloration of females

Frosty is a rare gene and responsible for the sexual dimorphism in Thuringian Self Pigeons. Frosty has special characteristics among the known recessive sex-linked factors. Unlike dilution and the also recessive genetic factors reduced and rubella, frosty does not show in the female. Therefore typical for the breed are bleached ground-colored cocks and blue-bar and blue-check females.

Source: Axel Sell, Pigeon Genetics. Applied Genetics in the Domestic Pigeon, Achim 2012.

If a diluted-colored cock with a non-diluted hen produces sex-linked dilute females and intensively colored cocks, a frosty cock with a female that does not possess the frosty -trait will bring exclusively young without signs of frosty. Like shown for the ground-colored cock and his black hen without this factor and their blue and black young in the author’s loft.

Source: Axel Sell, Genetik der Taubenfärbungen, Achim 2015.

Frosty as a modifier

Frosty acts in certain genetic constellations as a modifier that alters the action of other genes. This could be followed on the example of Rubella. Rubella is also a sex-linked recessive factor but not a Frosty allele. The hemizygous females, who possess the rubella factor only once, appear in the bar and check variety, like the cocks with rusty-reddish rubella-colored bars or checks.

Source: Axel Sell, Pigeon Genetics. Applied Genetics in the Domestic Pigeon, Achim 2012.

Reduced is an allele of rubella and in the bar and check variant usually much lighter colored than rubella.

Source: Axel Sell, Pigeon Genetics. Applied Genetics in the Domestic Pigeon, Achim 2012.

The combination of Frosty and Rubella in a check female resulted after finishing the molt, in a delicate reddish color of the bars and check patches, as known from some Reduced.

 

Rubella-Frosty hen in the juvenile plumage and after the molt

The observation has meaning beyond the concrete case. If recessive modifiers can so easily turn the appearance of genetic factors into that of an allele, then it can also be so in other genetic constellations and with other genetic factors. Thus the question becomes acute how to decide e.g. at the variants of Recessive Red whether they are alleles or modifications and that is of relevance also for other traits.

Frosty and grizzle

A modification in the literal sense usually is considered a small effect. Frosty in conjunction with the grizzle trait has a far greater effect, as Frank Zetzsche has found in his experiments with Thuringian Selfs. Hemizygous Frosty females with the grizzle factor are typical blue grizzles. Homozygous Frosty-cocks with the grizzle factor, however, were almost white even being only heterozygous for the grizzle factor.

Source: Axel Sell, Genetik der Taubenfärbungen, Achim 2015, Schwerdt/Ziegler 1866.

Thus in the moment it seems impossible to breed them on a pure frosty base that is common in the other colorations of the breed. Blue grizzles, owlish in brackets in the standard, thus takes on a special status in the breed. To exclude them simply, however, is not conceivable given the history. For among the colorations listed by Ludwig Storch in 1856 in the pigeon fanatic town Ruhla in Thuringian ‘owlish’, ‘white owlish’, ‘black and silver owlish’, and others were explicit mentioned, how different they may have been from each other. It remains interesting to get further insight from coming breeding experiments.

Literature:

Pigeon Genetics. Applied Genetics in the Domestic Pigeon, Achim 2012.

Genetik der Taubenfärbungen, Achim 2015 (vergriffen)