Mutations that make no difference to the fitness of the phenotype are called:

1. The genetic changes caused by mutation can have one of three outcomes on the phenotype. 2. A change can help, harm, or make no difference at all. 3. Many mutations will also have no effect on the fitness of the phenotype; these are called neutral mutations. 4. Lethal mutations are the opposite extreme. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 18 'Evolution and the Origin of Species', sections 18.1-18.3_