Genetics of Lutino/Albino

Summary:
Ino - sex-linked recessive
Normal - dominant

Lutino/albino (ino) is a sex-linked mutation. This means that the gene is located on the x-chromosome. Male budgies have two x-chromosomes (XX) and female budgies have an x-chromosome and a y-chromosome (XY). Since the gene is recessive to normal, male budgies must have two ino genes (one on each x-chromosome) to be an ino variety. However, since female budgies have only one x-chromosome, if their x-chromosome has the ino gene, they will be the ino variety. It is because females need only one gene to express the trait that sex-linked mutations such as ino are more common in female budgies. Here, we will represent the ino gene on the x-chromosome as "Xⁱ" and the x-chromosome with the normal gene as "X". There are three genotype possibilities for a male budgie:

• XX - Two normal genes resulting in a normal male budgie.
• XXⁱ - One normal gene and one ino gene resulting in a normal male budgie that is split for ino.
• XⁱXⁱ - Two ino genes resulting in an ino male budgie.

And there are two genotype possibilities for a female budgie:

• XY - A normal gene resulting in a normal female budgie.
• XⁱY - An ino gene resulting in an ino female budgie.

Below are some punnet square examples of pairings. As you will see, if your goal is to breed a sex-linked mutation like ino, besides breeding two visually ino budgies, the best results will be from the pairing of a male who is split for ino to an ino female.