Other forms: pleiotropies
When a single gene affects more than one trait in an organism, that's known as pleiotropy. It's genetic pleiotropy that makes dogs with mottled, bluish-gray coats more likely to also be deaf and blind.
Pleiotropy is most obvious when something goes wrong in an organism, causing a mutation in a gene that affects multiple characteristics. In the human disorder known as PKU, a defect in one gene causes cognitive disability, eczema, and pale skin. Some chickens have a gene that causes them to lay fewer eggs, but also gives them frizzled feathers and a high metabolism. The Greek root of pleiotropy is pleiōn, "greater in quantity."