Genetics in praxis

Cross tables

Cross-tables are representations of the possible breeding results of pairs. This pairs are mated by the bird fancier to get specific outcomes, specific colour varieties like a yellow pastel, a rose opaline, and so on. In the cross-table all possible matings and the expected outcomes are written down. It is an easy to use resource for the aviculturist. The cross-tables are presenting single- and combined mutation factors and the possible colour varieties.

Using cross-tables
1. When we use the cross-tables we should have in mind our goal for the breeding season
2. We take the cross-table for the single or combined mutation factor for the colour variety we want to breed
3. We make a note of the ring numbers of the birds we have in stock, available for this specific goal
4. We make a not of the mutation factors they have, visible in the plumage and the split factors.
5. We search in the selected cross-table for the best combination.

1. The goal is pastel
2. Suppose you have two wildtype Bourke’s, a cock and a hen, both split for pastel
3. Control the split factor in your administration
4. Look in the cross-table below

Comments: The cock is always placed in the first column. In this cross-table there are three possibilities, the cock is pastel (cock 1), split pastel (cock 2) or wildtype without the pastel factor (cock 3). In principal it is possible to make nine different combinations.

Results: In the example, we mate the split cock and the split hen. In the cross-table: cock 2 x hen 2.
The possible result of this mating we find in the vertical column under hen 2, and the horizontal row next to cock 2. The result of this mating we will find in the centre of the grey cross, the dark grey part of that cross.
There we see: a pastel cock, a wildtype cock split for pastel, and a wildtype without the pastel factor. We see : a pastel hen, a wildtype hen split for pastel and a wildtype without this factor.

In the example we reach our goal, it is possible to breed from this combination pastel, cocks and hens. But we were creating a problem. Some of the wildtypes are split, but others don’t have this split factor. The wildtypes are looking the same, we cannot see if the wildtype is split for pastel ( /p) or not (-).

Cross-table Y-3: Pastel, Inheritance resessive


In this cross-table (above) we can easily see which combinations are good, which combinations are better to avoid.
-cock 1 x hen 2 and cock 2 x hen 1, are the best combinations, we have pastel and we can use all the wildtypes because are all of them are split for pastel
-cock 2 x hen 3, cock 3 x hen 2, cock 2 x hen 2 has to be avoid, because of the wildtypes.
-cock 1 x hen 1, give pastel also , but I don’t like the combination of two birds with red eyes. Eye sight problems are possible.
-cock 3 x hen 3 have of course no splits at all.

Colour: In the yellow boxes of the table the useful (light yellow) and best results (dark yellow) are represented.

Comments: In the comments of the cross-tables the best results are discussed. When you are accustomed to use percentages it is easy to get them. When there are four possible results of a certain mating the chance that one of the outcomes is realised is 100:4=25%. When there are six possible results, the chance is 100:6=16,6 %. Etc.

Pastel is the name for the characteristics of the eumelanin only. There are other colouring factors. Yellow pigment inherits intermediate. So you can select a cock and a hen. In the wildtype you inspect the margins of the wing coverts. In the pastel you select the bird with the most yellow pigment.

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Copyright 2003 by Bob Fregeres