Wonder bags and their genetic decoding

The importance of case studies for the understanding of hereditary processes

The black pigeon and his platinum-check hen are a 'wonder bag' in breeding. Five colourings in nine kittens! Coincidence or genetically explainable? It is a coincidence that just these colourings fell in the respective numbers. The fact that they had to occur with a certain probability due to the genetic disposition of the parents can be explained by hereditary laws. One can even deduce probabilities for the next breeding season.

Who cares about that? Some will say, I don't know the breed. The colourings also seem strange to me. Whoever thinks like that should not read genetic texts. He can only be disappointed. For there is no special genetics for a breed, only an application of genetics to breeds and traits. Educators speak of exemplary significance in learning content. In primary school, the multiplication task 15 times 13 is not set so that children remember the result for the rest of their lives. The methodology of written multiplication and mental arithmetic is understood and practised: methodological competence, not the memorisation of results!

It is similar here. Using the example of the breeding pair, those interested can activate their knowledge of Punnett's squares. They can reconstruct the hereditary processes for the relevant hereditary factors. The 'genetics staircase' composed of the respective squares provides a framework for systematically 'working through' the individual steps. In summary, it leads to the answer to the question which colourings can be expected from a mating and with which probability. In the planning stage it provides the framework for systematic breeding planning. Be it to avoid too close inbreeding by occasional crosses when breeding with several colourings, be it to transfer breeding progress from other colourings or breeds.


Fig. 1: Platin check hen and black cock

Genetics of the parents: The sire is heterozygous for the colour spread factor S. He is at least heterozygous, but probably homozygous for the bar pattern covered by Spread. Finally, he is heterozygous for the recessive hereditary factor platinum. The dam is homozygous platinum, mixed hereditary check/bar. She does not have the spread factor. Although late mated, until now (August 2022) nine youngsters in five colourings: three blue-bar, three Spread platinum, one blue-check, one platinum-check and one platinum bar.

Didactics: The methodical procedure in explaining the diversity of the offspring can be illustrated by the image of the 'genetic staircase' formed by Punnett's squares. Individual 'building blocks' of the respective step are examined with known hereditary laws. The partial results are combined, taking into account overlapping (epistatic) effects and, if necessary, genetic linkages. Finally, the summarising result is read off.

Fig.2: Genetics staircase adapted to the problem

On the genetics of the offspring on the individual steps:  Let's start 'going through' the 'stairs' at the top step. From the mating 50% offspring with the dominant colour spread factor Spread are to be expected (S//+), which they inherited from the sire who is also heterozygous for Spread. 

At the intermediate level in the analysis of the inheritance of platinum, 50% should be homozygous for the recessive factor platinum (pl//pl) in a large number. Here it is 5 out of 9.

Finally, at the lower stage in the patterns, 50% are expected to be barred (+//+) and 50% checkered (C//+). Because of the epistatic (overlapping) effect of spread over the patterns, the pattern is clearly only visible in juveniles without spread. In the presented mating there are 4 barred and 2 checkered. However, the experienced breeder will have a reasonable suspicion in one of the three kittens with the spread factor that the colour spread factor hides the bar pattern.

Not all possible colourings have fallen out of the magic bag yet. Solid black is still missing. The probability for black was . Instead of the expected 1/8 blue bars, 1/3 have fallen.

The genetic make-up of the bred kittens:

         The three blue kittens are mixed platinum (+//pl) with the bar pattern and without spread.

         The three solid coloured platinums are homozygous platinum (pl//pl) and heterozygous spread (+//S).

         The blue check one is mixed platinum (+//pl), mixed checkered (C//+) and without spread (+//+).

         The platinum check female is purebred platinum (pl//pl), mixedbred checkered (C//+) and without spread.

         Finally, the barred platinum male is pure platinum (pl//pl), also without spread (+//+).

Exemplary meaning: The illustration can be transferred 1:1, e.g., to the mating of silver (spread milky) Lahore with barred and checkered milky as well as with the initial colour strokes. The word platinum is only to be replaced by milky. One can easily make a modification to the dominant factor indigo to include Andalusians. It is also easy to integrate sex-linked factors such as Stipper, Reduced and Rubella by adjusting the squares.  Above all, one should realise how easy it is for initially astonishing breeding results to explain themselves with a structured approach. The real benefit of the systematic analysis, however, does not lie in an explanation of the past, but in the implementation of the gained competence for breeding planning.


Fig. 3: Blue bar youngsters


Fig. 4: Spread Platinum hens


Fig. 6: Blue check, Platin check and Platin bar

Concluding remarks:

The didactic concept related to the current breeding activities in the author's loft has proved helpful many times. It was already used as a leading idea on the cover of the first brochure on pigeon genetics as a staircase-shaped sequence of Punnett squares preceding the text. It can currently also be found on the covers of the introductions to pigeon genetics published in French, Dutch and English. A chance to familiarise yourself with the implementation of inheritance rules in practice in a playful way with examples and exercises given as supplement.