A little history
As we know today, Gregor Mendel, best known for his experiments with peas, was the basis of genetics. He demonstrated through his experiments that if he crossed two peas (F1) with different characteristics such as flower color, leaf size ... Then the offspring (F2) kept the characteristics of a single parent. All the flowers of these young peas had the same color and size of leaves.
It’s as if they “lost” one of the properties. When he crossed these young F2 peas with each other, the F1 characteristics reappeared among the offspring of the F3 generation. Mendel called these characteristics shown by F2: Dominant. And the characteristics hidden in the F2 have been called recessive.
Currently we still call it dominant and recessive. However we do know that Mendel discovered "complete dominance". There are indeed other forms of dominance. We already know these forms so we will mainly bring a few provisions to remember.
We know that genes carry characteristics and that these genes are located on chromosomes. There are genes that deal with the color of the eyes, the color of the legs, the size of the beak… Chromosomes are found in the cells of the body: They are stored in the nucleus of each cell. In each nucleus of each cell are the genes for the color of the eyes, the color of the legs, the size of the beak ... However, the functioning of the “color of the eyes” genes is manifested only in the eyes. In the paws, the "eye color" genes do not show up. Each cell therefore “knows” where it is located in the body and which genes it must activate.
Chromosomes go in pairs, all genes are found in pairs. So for the eye color gene, we have two genes. This also applies to the color of the legs, the size of the beak ... These two genes for the color of the eyes can cause a color of the eyes blue. It is also possible that one gene is responsible for the color blue and the other for the color brown. (which does not mean that the being will have one blue eye and the other brown, the brown of the eyes is dominant over the blue, so both eyes will be brown).
Why are the mutations in zebrafinch of pale back, masked (new type) and masked old type combined with each other so difficult to predict !?
Quite simply because we cannot speak at the genetic level of different mutations but rather of allelic versions of a single gene. The pale back, the masked and the old type mask are due to the same gene but which has three allelic versions.
To understand well let's make the parallel with man, the color of the eyes for example, whatever our eye color, our iris color and coded by the same gene, but this gene has many different versions (alleles) which allow us to have the color panel that we know.
Now that we know a little more about what complicates these crosses, let's take a look at how each allele behaves in relation to each other.
Everything is a story of dominance and co-dominance or recessivity.
A small table to illustrate all this :
Allele / allele Pale back Masqued Masqued OT Pale back x Pale back Pale back Masqued Pale back x Masqued Masqued OT Pale back Masqued x
*OT = Old type
In this double entry table you can see that it allele dominates the other, the bird will therefore have the phenotype of the allele which dominates, be careful, it is not because the allele is dominated that it does not not influence. See pale back / OT mask, the back is more diluted because of the masked OT allele.
From this result we can draw the first conclusions :
- The pale back can be masked or OT masked.
- The masked can be a masked OT split but cannot be a pale back wearer (pb dominates masked = pb / masked). *pb = pale back
- The masked OT cannot carry a pale back, nor a masked person because the latter two dominate him.
The aim of this article is not to establish an unstoppable rule for the recognition of a gray male split (carrying) the black breast mutation. Rather, it aims to gather the clues that will allow you to identify it.
For this, every detail of the mutation is taken over, according to what I observed during the selection of my strain of gray black chest.
Before starting to analyze each possible clue, it seems important to me to bear in mind that the black chest mutation changes the shape of the drawings. To identify a split of the black chest mutation, I also advise you to take into account all the clues described in this article.
Let’s proceed and analyze the phenotype of a gray black breast from the head to the rectrices in comparison to a gray split the black breast mutation. To identify each descriptive term used, you can use this diagram : Descriptive terms in zebrafinch.
1. Mustachial line
Black chest : The moustachial line will be pronounced and intense black.
Split (/) Black chest : The moustachial line may be more pronounced than on a gray, however this does not constitute for me a sufficient clue.
2. Tear line
Black chest : The tear line disappears (ideally according to the standard) or only a fine line remains.
Split (/) black chest : Different cases depending on the force of expression of the mutation in the split.
- The tear line is present and fine :
- Tear line is present and wide :
- In some cases, the tear line of a split black chest may also be absent. It will be necessary to rely on the other clues to know if it is a split or a black breast in its own right.
Black chest : The drawing of the cheeks will extend up and back of the head.
I made this glossary to illustrate in photos the existing mutations in the zebrafinch.
He can help you identify the mutation (s) of your zebra finches.
Important precision :To identify the genotype of your zebrafinch, it will be necessary to take into account that a zebra finch can carry a mutation without being mutant.
Being a carrier (/, split) of a mutation means that it is partially present (genetically speaking). From the visual point of view the partially carried mutation will not be seen or only by some clues present in the appearance of the bird.
In this case, it will be necessary to have a trained eye to determine the genotype. Sometimes check couplings will be necessary.
Your zebra finch can also have several mutations, the possible combinations are numerous.
This glossary is based solely on the phenotype (visual characteristics) and single mutations (not combined).
The gray zebrafinch is not a mutation, it is the original (wild) type.
1. Gender-related mutations
The female can never be a split, so she is either mutant or non-mutant.
The male can be a split of the mutation.