A dilution gene is any one of a number of genes that act to create a lighter coat color in living creatures. There are many examples of such genes:
Two rats: left: agouti, right: coat lightened to blue by a dilution gene
Great Danes lightened from black to blue by the dilute gene.
Doberman: black with tan in the back, blue with tan in the front. The light brown areas were hardly lightened at all
Blue-light brown brindle dog
Canine follicular dysplasia
Follicular dysplasia is a genetic disease of dogs causing alopecia, also called hair loss. It is caused by hair follicles that are misfunctioning due to structural abnormality. There are several types, some affecting only certain breeds. Diagnosis is achieved through a biopsy, and treatment is rarely successful. Certain breeds, such as the Mexican Hairless Dog and Chinese Crested Dog, are bred specifically for alopecia.
A greyhound with bald thigh syndrome, a form of pattern baldness seen in this breed
Seasonal alopecia
Color dilution alopecia in a fawn doberman. The close-up of the leg shows the characteristic sparing of the tan color points in this syndrome, only fawn hairs being affected.