The broken locus has two possible genes: the incompletely dominant broken gene, referred to as ‘En,’ or the recessive, solid gene, notated as ‘en.’ This locus determines whether the fur color is expressed over the whole coat or not.
The ‘en’ solid gene has no impact on coat color expression. It causes the fur pigment to be produced normally according to the other alleles. Because it is recessive, the rabbit must be homozygous for ‘en’ to be considered solid. Since solid coloration is so prevalent, however, the term solid is often omitted when describing the coloration of a rabbit with ‘enen.’
The ‘En’ broken gene stops the production of fur pigment on the rabbit’s hair shaft over the body, causing blotches of white, creating a ‘spotted’ rabbit. When a rabbit contains the pair ‘Enen,’ the rabbit has at least 10% of their fur producing color pigments, and is referred to as having a broken coloration. For example, a Netherland dwarf with the genotype ‘aaBbCCddEE Enen’ would be labeled a broken blue self. There are three broken patterns identified by the AMLRC that result from ‘Enen’: the Blanket Pattern, Patches Pattern, and Spotted Pattern.
For a broken mini lop to be showable, they must have a butterfly nose marking; a partial nose marking is a fault. When ‘En’ a rabbit inherits the pair ‘EnEn,’ only 10% or less of the rabbit’s fur shafts produce color because the En gene is incompletely dominant. This is referred to as a Charlie coloration.
Partial Nose Mark
References: hickoryridgehollands.com/blog/2017/8/3/the-broken-gene, AMLRC handbook