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The exploration of the genetic basis of pigeon colors

 Learning by doing works sometimes. For complex questions about color inheritance in pigeons rather not. It usually ends in the conviction that the general inheritance laws do not apply to pigeons. Scientists also took several decades after 1900 to obtain a satisfactory classification of color classes. Before 1900, the color gradations from black to white with their transitions were described in great detail, e.g. in the book from Prütz of 1885. Black was demarcated from blue. Blue was split into nuances such as lighter and darker blue, silver and more lightening. Among them, today surprising, also ash red red and ash yellow. Red, yellow and brown colors, including bronze varieties, formed another group.

The process of enlightening of the genetic composition of the basic colors

Leon J. Cole (1877-1948) was the first professor of genetics at the University of Wisconsin. He showed in 1914 that there were two types of red, one dominant red and one recessive. That sounds trivial, but it was groundbreaking. Before, you could not tell the two types apart. So there were unexplained contradictions in hereditary experiments. It was discovered in the research group of Cole that blue and black have the same basic color. It was also recognized that Dominant Red was something else. Jan Metzelaar, a Dutchman who worked at the University of Michigan, reported in 1924 on brown as an independent base color. It was only around 1930 that the epistatic character of Recessive Red over the three primary colors was confirmed. In Fig. 1 they are therefore found under all three primary colors. Besides the scientists mentioned many others were involved in research, from different institutions worldwide. In parallel, bronze, the dilution, feather structures and others were investigated.


 

Fig. 1: Time Chart of the Exploring the Relationship between the main Colorations (Source: Sell, Genetik der Taubenfärbung (German language), Achim 2015).

Exercises

The development of the classification of the basic colors took about three decades. Building on the state of knowledge, with suitable teaching material it requires a day to understand the classification according to genetic criteria. It takes a pencil and some paper to use the Punnett square as a didactic aid to understand the results of color crossings and use them for breeding planning. However, it is useful to start on the first page of teaching materials, not in the middle.

It is then easy to explain why, in addition to black young cocks, a yellow male and a black female suddenly have dun female juveniles in their nest and that Mendel's 'Uniformity Law' has been repealed. Fig. 2 is in a photomontage of Ancients (the blacks from 'Gieseke World' and shown at the 3rd German Tumbler Show). But the results shown can be reconstructed at any time with other breeds in one's own loft.

From a genetic point of view, it was not, as beginners suspect, only a yellow cock paired with a black hen. The basic color of most of the Recessive Reds and their dilutes, the Recessive Yellows are black and most have the color spreading factor S as the blacks. From a genetic point of view, from the base color black was paired with black, which results in a black base color in offspring.

From a genetic perspective, on a second level, Recessive Red was paired with Non-Recessive Red. From the investigations of Cole et al. we know that the recessive red and thus the yellow are epistatic to the basic color. With homozygosity present, it has covered the black ground color in the yellow cock. Paired with blacks, which we assume is not accidentally mixed with recessive reds, only heterozygous recessive reds will come out of it. They, since recessive, will not show the red color.

Yellow is a dilute color. The dilution factor is inherited sex-linked recessive, as already noted in 1913 by the Englishman Staples-Browne. This brings into play the sex-linked inheritance that Mendel did not experience. From a diluted-colored male all young females will inherit the dilution factor and appear dun at black primary color. Their brothers are only heterozygous for the dilution factor, and as this is recessive, they will not show it. With black basic color they are also phenotypical black.

Exercises with Punnett’s Square

At the first level of observation, the genetical base color, both the yellow and black have a black base color. The two genetic information of the cock are entered before the first column of the square, the genetic information of the hen in the header. The four cells of the inner square contain all theoretically possible combinations. The base color is like the dilution sex-linked. Therefore, the Punnett’s square with a 'dot' is chosen for the 'hemizygous' females. They only have sex-linked one gene for color. Instead of the symbols here the cursive is used. The youngsters are all black from the primary color. Trivial, for beginners however is the idea that an intense red or yellow hen could genetically have a black base color, already hard to understand.

Fig. 3: Punnett Square for Color

The second level of consideration is the recessive red, which is to be considered in the Punnett square for non-sex-linked genetic factors.

 

Fig. 4: Punnett's Square for the Recessive Red

All juveniles are only heterozygous recessive red, so that the factor cannot affect.

At the third level of consideration we return to the Square of sex-linked genes. From this point of view, a dilute-colored male is mated with a non-diluted female. The female can only have one hereditary information, which in the black female is the wild type, non-diluted. The cock has twice the recessive dilution factor:

 

Fig. 5: Punnett square for dilution

In female youngsters, only the genetic information dilution appears, so they are also diluted in appearance. In contrast, the cocks are only heterozygous for dilution, but they will not show up since it is a recessive factor.

Combination of viewing levels

The young females have a black base color, they have the recessive red only heterozygous and are diluted. Thus, they are of the phenotype dun colored.

The young cocks have also a black basic color, also the recessive red in heterozygosity. Unlike the females, they are only heterozygous for dilution. This makes them phenotypically black.

If you want to test your understanding, you can try to figure out the result that would have been expected if the black Ancient hen had been mixed for recessive red. If you also want to train your dexterity on Punnett's square, you can use the square to try to figure out what it means for the inheritance of crest and to find out the hen's genes with regard to crest, if some of the offspring like in the montage show a crest.

Literature:

Axel und Jana Sell, Vererbung bei Tauben, Reutlingen 2004

Axel Sell, Pigeon Genetics, Achim 2012

Axel Sell, Genetik der Taubenfärbungen, Achim 2015

www.taubensell.de