I am trying to learn about chicken genetics and have some questions. From what I understand there are four major alleles that control comb variation; rose, pea, duplex - V, and duplex - buttercup. I was looking at this comb chart and noticed that the different comb types shown are only caused by a single allele, or in the case of strawberry, cushion, and walnut are all from the same combination of rose and pea. What happens when rose and one of the duplex alleles are combined? Or pea and duplex? Or rose, pea, and duplex? Is there a chart or book that details all of the possible comb variation?