Theoretical expectations in matings with
A partial dominant; non-sex-linked mutation

Frank Mosca

(Genetics Symbol - In)

Partial dominance means that the mutation shows up in a different form when in a heterozygous state than when in a homozygous one.  In the case of indigo, a heterozyous bird has bronzy wing bars, a somewhat washed out tail bar, usually darker rump and neck blend - indigo colored.  In the homozygous state, a bird can actually be mistaken for an Ash-red, though the neck blend and rump tend to be darker in homozygous indigos than in Ash-reds.
Since Indigo is not sex-linked, it makes no difference if the cock or the hen is carrying it for these tables to show percentage expectations.  Remember, these ARE just expectations.  You may well get five wild-type young in a row from the first mating or five homozygous Indigo.  However, over the course of about 100 or more birds bred, the percentages will fall out into just about those predicted.
Heterozygous Indigo X Heterozygous Indigo
Genetics Formula
In//+    x   In//+

In +
 In In In In +
  + In + + +
25% Homozygous Indigo which is often an ash-red mimic.

                                                       50% Heterozygous Indigo
                                                       25% non-Indigo (wild-type)
By adding Spread to the In+ birds, you get andalusian. Andalusian is simply a fanciers term for the combination effect of heterozygous Indigo with either homozygous or heterozygous spread. Homozygous indigo with spread is NOT andalusian either in name or color.

 Heterozygous Indigo X Wild-type (non indigo)

Genetics Formula
In//+    x   +//+

+ +
 In In+ In +
  + ++ + +

50% Heterozygous indigo.
50% non-Indigo (wild-type)

Homozygous Indigo X Homozygous Indigo
Genetics Formula
In//In   x  In//In

In In
In In In In In
In In In  In In

100% Homozygous Indigo

Homozygous Indigo x Wild-type (non indigo)

Genetics Formula
In//In  x +//+


+ +
In In + In +
In In + In +

100% heterozygous indigo
(If you happen to have mated the homozygous indigo parent to a homozygous spread bird, then all the youngsters would be andalusian colored (heterozygous indigo and heterozygous spread)