- Basic Concepts
- DNA & RNA
- Simple Inheritance
- Modify Mendelian Ratios
The final color of the mammalian coat depends on a large number of variable factors, themselves interdependent. Ultimately, the composition, numbers, shape and arrangement of the pigment granules can all influence the final result, as can chemical changes to the eumelanin itself.
For example, black Labrador Retrievers (with the genotype B-) produce dark eumelanin, while chocolate Labs (bb) have a mutation in one of the last steps of eumelanin synthesis, which results in the production of a lighter brown pigment.
In mice, the dilution (D) gene can further modify these colors. Mice with the 'dd' genotype have misshapen melanocytes that produce relatively few, large pigment granules that tend to clump together. The overall effect is to produce a washed-out, lighter color in the hair (even though the pigment itself is unchanged).