Pale back, masked, masked old type, 3 allelic versions

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 :

*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.

To know :

• Each bird has two chromosomes so it has the same gene twice (but not necessarily the same allele).
• The pale back, the masked and the masked OT are mutations linked to sex, they are therefore carried by the sex chromosomes, in birds the male has twice the same sex chromosome (ZZ) and the female has two different sex chromosomes of which only one carries the genes linked to the phenotype (ZW, the W carries the genes linked to the phenotype).

Now let's detail each possible coupling, let's start with the pale back and the masked one :

Male pale back X masked female

This coupling gives: 50% male back pale / masked; 50% female pale back.

Masked male X female pale back

This coupling gives: 50% male back pale / masked; 50% masked female.

Male pale back / masked X female pale back

This coupling gives: 25% male pale back; 25% male pale back / masked; 25% female pale back; 25% masked female.

Male back pale / masked X female masked

This coupling gives: 25% male back pale / masked; 25% masked male; 25% female pale back; 25% masked female.



Now let's approach the case of the blade back and the masked OT : The results are identical to the blade back X masked coupling, you just have to replace masked by masked OT.
Finally, let us approach the case of the masked and the masked OT: The results are identical to the case of the dp and the masked, it suffices to replace pale back by masked; and masked by masked OT.

Example: Male pale back X masked female

This coupling gives: 50% male back pale / masked; 50% masked female.

After transformation: Masked male X masked female OT.

This coupling gives: 50% masked / masked male OT; 50% masked female.

Make way for a few different cases:

Male back pale / masked X female masked OT

This coupling gives: 25% male pale back / masked OT; 25% masked / masked male OT; 25% female pale back; 25% masked female.

Male back pale / masked AT X female masked

This coupling gives: 25% male back pale / masked; 25% masked / masked male AT; 25% female pale back; 25% female masked AT.

Hopefully this article will make you more comfortable with the three mutations of Paleback, Masked, and Old Guy Masked.