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)
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