Talk about the intermediate heritage
If you ask at a meeting of zebrafinch lovers questions about the genealogy of the masked, pastel, or black cheeks, we are certain to receive the correct answer.
But if we ask the genealogy question about the format (size), the shape of the head or the length of the beak, the answers will be multiple and different.
Some will say intermediate, others dominant, etc.
Nevertheless these characteristics follow the laws of Mendel. Many breeders do not believe this explanation, but it is true. It seems that laws no longer behave strictly as in other color mutations. A wider variation in format (size), shape of the head, etc ... seems normal.
In nature, we find in zebrafinch the same variation in the format. And, in the process of domestication, this difference in variation has increased. Our cultivated zebrafinch are on average two centimeters wider than their ancestors in the wild.
In articles, one always recommends a hard selection at the level of the format and the model taking into account the differences between the parts like the head, the body, etc.
But the format and the model are directed by the genealogy. The body shapes are driven by factors.
The question is: Is there a relationship between the different factors that governs the format, the model, the shape of the head and the beak ?
In my opinion, these factors are independent of each other. Lesser quantities of zebrafinch are found in the correct size and type of beaks, and there are no good-sized zebrafinch; the right kind of beak alone, etc. This is not an advantage in breeding a good size and hard selection is the only way to improve these characteristics.
On the other hand, we know that factors can influence the results of others : They can modify the result, strengthen the result or reduce the result.
We are aware that several factors must work together to achieve a good format. Factors help each other to manifest together. They are called polymer factors. These factors drive the format and size.
The explanation of Hans Kloren, in his book : "The coupling of a beefy zebrafinch to a zebrafinch of small size, gives us young intermediate size.If we coupled these young people, we would expect the following results : A quarter shows the sturdy size of the first parent, one quarter shows the small size and the rest looks like the young F1 This is not true, it is even exceptional if part of the F2 game is similar to the strong parent.
What is the explanation ?
Suppose the beefy parent has 4 pairs of factors in the format that are different from that of the small parent. The 4 factors provide part of the format. The young zebrafinch must in this case have a large format. The first generation of youngsters (F1) will have the intermediate format because these youngsters receive from both parents a factor of each pair. According to Mendel's laws, the next generation (F2) will show all possible combinations of factors, which is the case in reality.
In the generation F2 we will find few copies that possess, of four factors, the one that offers the possibility to have a good format. The calculation of chances is the same as the calculation of the "color" factors. Starting from 4 factors, the possibilities of combining are enormous. The chance to find the 4 factors together is one in 256. If the format is headed by more than 4 factors, the chance decreases exponentially. The reasoning for the model, the type of beak, etc. is the same.
The fact that most fans are convinced that the format is inherited in an intermediate way, is based on the fact that the format of the F1 generation is in the middle of the formats of the parents. Intermediate means between the two. It is true to say that the format does not inherit intermediate, but that the format presentation of the F1 generation is intermediate.
Hans Kloren assumes that the factors responsible for the format and the model are recessive factors. In many cases, this is true. But this is not true for all strains. Some strains give completely different results. Those who bought Dick Offerman zebrafinch had other results by entering these zebrafinch into their stock. The format and model of this strain were dominant and gave the F1 and F2 generations zebrafinch similar to the starting zebrafinch.
An example : Luk P. bought, in order to manage a symmetrical strain of variegation, two subjects with a thin head. He never knew how to remove this fine head from his stump: This form was dominant.
In most zebrafinch, the format and pattern are composed of recessive polymeric factors, but in some strains we find similar factors (composing the format, the model) playing a dominant role.
Jan Van Looy
Article written in 2007.