The answer to this paradox is recombination. Pairs of chromosomes line up during the cell division events that create gametes and switch pieces with each other. Thus breedings to a bicolor dog that isn't merled should only be able to produce sable merles and tricolors, but never blue merles. But we observe that breeding a trifactored sable merle to a bicolor produces sable merles, trifactored sables, tricolors, bicolors, and blue merles - combinations that couldn't occur if the genes were on the same chromosome. Examples of how genes work Mechanism of heredity understood at level 2 - DNA stores information, transcribed to RNA, RNA translated to protein.
Mutations change gene product.
Structrural Genes - Type I Collagen. Proteins have shapes. Proteins can assemble in groups to build larger structures. Genes Doing Something - Hemoglobin Proteins don't do it alone. Single base pair changes can alter a protein's function, or not, depending on where they are.