Explanation of Recessive Inheritance in Zebra Finches

This is a diagram of recessive inheritance. I chose Pied since it is a common color variety, but any of the recessive traits would be inherited in the same manner as described above. The yellow circles (bb) indicate the genes for Pied, the blue circles (BB) indicate the genes for the dominant Grey gene. When bb is crossed with BB, all of the offspring in the first generation will have the genetic makeup of Bb, the green circles, one gene for Grey and one for Pied. Since Grey is dominant, and Pied is recessive, all of these birds will show only the Grey color, but they carry the Pied gene. Hence they are termed "Split" for Pied. Any bird which is referred to as Split, therefore, carries a hidden recessive trait. When two birds that are split for Pied (Bb) are crossed as in the above second mating, the various genes for Grey and for Pied segregate and a percentage of the offspring will show the Pied coloration. In all recessive traits, when two split birds are interbred, the ratio of their offspring will be three dominants and one recessive. In this instance, the second generation cross produces three normal Greys and one Pied. Notice that in the second generation offspring, there is one Pure Grey(BB), two Greys which are split for Pied(Bb), and one Pied(bb). These expectations are typical for all recessive traits.


This is a diagram of recessive inheritance similar to that in the previous chart, with one exception. In this mating in the second generation, a Pied hen is used instead of the Normal split to Pied hen. The results are slightly different. Notice in the second cross offspring, two Greys (Bb) and two Pieds (bb) are produced, making the ratio of 50% Grey and 50% Pied.

Whenever you cross a split bird to its recessive counterpart, (example: split Pied X Pied) the ratio of dominants and recessives is 50:50. The previous cross produced only 25% Pied. This rule applies to all recessive traits.

These plates and information are from my book, Varieties and Genetics of the Zebra Finch.