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How to explain it:
Combinatorial and epistatic effects in color genetics of the
domestic pigeon
The rich palette of pigeon
coloring is the result of combinations of color factors. If these
are known for the parents, one can predict the probability of
certain colors appearing in the offspring. The methodical principle
can be learned from every color group. Shown here as an example in
our own breeding.
Currently in the nest are a
black and a platinum youngster. In the previous clutch a solid
platinum colored cock was bred. The father is genetically of black
color base and is also phenotypical a solid black. His parentage is
heterozygous for the recessive factor platinum. Genetically, in
addition to the genetic code for the black base color, it has the
dominant color spread factor (S), at least heterozygous. Only Spread
turns blue and blue checkered pigeons, which also have a black base
color, into black ones. Since the cock has a barred (non-spread)
youngster, he is heterozygous for S. S covers (epistatic) the
pattern. In the family, only bars and the dominant check are present
as pattern. From the appearance of the parents, the cock is probably
at least heterogeneous for the check pattern. Both parents cannot be
homozygous, since otherwise no barred youngster could have been
raised. The solid platinum female has genetically, like the cock, a
black basic color. Recognizable by the barred young, also only
heterozygous for Spread. In the pattern for the same reasons as in
the cock, probably check/bar.
Fig. 1: Pomeranian Eye-Crested
Highflyer black cock and Spread Platinum hen
 
Fig. 2: From the pair in Fig. 1
young platinum with bars and black (left) and young platinum cock
with color spread in the moult (right). Spread Platinum cocks are
lighter colored than the females.
For many breeders it is a
single mating, a black with a platinum. From a genetic point of
view, there are several pairings at the level of the gene pairs
involved, which are initially examined separately (Fig. 3). Both
parents are homozygous for the black basic coloring (code for black
pigment). Thus, only individuals with the black basic color are to
be expected among the young. This does not have to be shown in
Punnett's square. Different with the color spread factor Spread.
Both parents are heterozygous. According to Mendel, half of the
young, like the parents, are homozygous for S (S//+) and show the
dominant factor S, a quarter is homozygous (S//S) and a quarter does
not have it. This quarter has bars or checks. At the platinum factor
level, the female is homozygous for platinum, the cock heterozygous.
According to Mendel, in such a constellation, half of the young will
be homozygous platinum (pl//pl) and will also show this in the
phenotype. The others will have platinum heterozygous. Since
platinum is recessive, they will not show platinum. Finally, in this
example, the pattern is relevant. According to the preliminary
information, both parents seem to be heterozygous for the check and
the bar pattern. Again, according to Mendel, from this you will get
half homozygous check young, one quarter homozygous checkered and
one quarter barred.
Fig. 3: Punnett’s squares for
the color spread factor, for the platinum factor and for the pattern
covered in pigeons with the spread factor.
If we combine the information
from the Punnett squares, we can see, among other things, in the
square of the color spread factor that only ¼ of the young do not
have the factor. By squaring the platinum factor, you can see that
half will be homozygous for platinum. The pattern square shows that
¼ of the hatchlings will genetically have the code for bars
(non-checks). However, in most of them covered by Spread (Fig. 4).
The barred platinum young
therefore is a rare occurrence. The probability is about ¼ x ½ x ¼ =
1/32. In the case of numerous offspring, there will still be
blue-bar, blue-checkered and platinum-checkered colorings.
Fig. 4: Exemplary combinatorial
effects of color genes taking into account the epistatic effect of
spread
Inheritance is conveyed here as
a logically structured puzzle. Other colors can also be viewed using
the same didactic principle. An accompanying booklet with tasks and
solutions was designed for the new edited English, Dutch and
French-language 'Introduction to pigeon genetics', with which you
can playfully familiarize yourself with the essential mechanisms of
pigeon genetics. The basic didactic principle for a different color
constellation is already prefixed on the cover, as it was on the
German-language brochure a few decades ago. As those in the know can
immediately see from the symbols on the cover, the mating presented
there with dominant red also involves a sex-linked inheritance (Fig.
5).
Fig. 5: Combinatorial and
epistatic effects as the guiding motif on the cover, Introduction to
Heredity in Pigeons (English, Dutch, French) 2022, and Inheritance
in Pigeons 1980
Literature:
Hollander, W.F., Origin and
Excursion in Pigeon Genetics, Kansas 1983
Levi, W. M., The Pigeon, Sumter
1941, reprinted 1969
Sell, Axel, Introduction to
Heredity in Pigeons with a supplement Comprehensive Questions, Achim
2022 (also in Dutch and French language)
Sell, Axel, Pigeon Genetics.
Applied Genetics in the Domestic Pigeon, Achim 2012
Sell, Axel, Vererbung bei Tauben, Traventhal
1980
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