09/24/2026
Ever wonder about blue egg genetics 🤓?
The blue egg gene comes from a very old mutation in the chicken genome originally caused by a retrovirus. The virus recoded the chickens DNA to deposit biliverdin onto the eggshell 🤯.
The blue egg gene is called the Oocyan gene or O, pronounced oh-oh-SIGH-an. 🥚
It’s an Autosomally dominant gene, meaning it’s not s*xlinked, and it will be dominant over no expression when heterozygous.
A chicken can carry 1, 2, or no copies of the O allele. 🧬
With 1 inherited copy it is called heterozygous. Since O is dominant it will express when heterozygous, all hens will lay blue/green eggs. 🪺
Hens that are homozygous inherit both copies of O and lay the greenest/bluest eggs! 🐔