You only need one dominant gene to have?

Dominance is not inherent to an allele or its traits (phenotype). It is a strictly relative effect between two alleles of a given gene of any function; one allele can be dominant over a second allele of the same gene, recessive to a third and co-dominant with a fourth.

this protocol provides a detailed procedure for co-immunoprecipitation (co-ip) to identify protein–protein interactions.