Gene is actually the basic tool of inheritance for any animal. Canines are of no exception. In canines like for any other animal, gene is the carrier of information in a biological system. However, any particular trait in your dog is actually not determined by any specific gene, but as a matter of fact a single trait in your dogs can be driven by a set of genes. Each single genetic character trait in German Shepherd, as in all other canine breeds is determined by a set of gene. Colors and patterns in dogs can be considered as one of the best instances for the fact that a characteristics can be determined by many genes, and not just only a single gene. German Shepherd Dog has many colors and patterns. This goes beyond all doubts that these entire range of patterns and colors in GSD or in any other dogs is the result of the roles of multiple genes, instead of just one. While a set of genes control the color or patterns in a dog, another set of genes determine the distribution of the patterns.
Alike almost all higher animals, dogs are also blessed with two sets of chromosomes one set from the dams side and the other set from the sires side. Dogs, alike Wolves, have 36 chromosomes in each set, which results an incredibly huge volume of permutation and combination of chromosomes. Hence, possibility of experiencing more than one litter-mates with exactly the same combination of chromosomes is hugely rare. This means two dogs (from same litter) almost cannot have all character traits (behavioral, physiological, and colors) exactly identical.