Edited by Triplehorn - 11/5/15 at 8:48pm
I am not an expert when it comes to chicken genetics. In general, however, f we are talking about simple genes, however, you will not be able to tell the difference between a homozygous dominant carrier and the heterozygous version of the trait without test breeding. Things get more complicated when it comes to incomplete dominance because there could be degrees of it. Are you sure that the trait isn't polygenetic?
Read post number two in this thread.