Final answer:
A loss-of-function mutation that shows a phenotype related to the mutant gene is an example of a dominant negative mutation.
Step-by-step explanation:
The loss-of-function mutation described in this question is an example of a dominant negative mutation. In this case, the mutant gene product adversely affects the normal, wild-type gene product within the same cell, blocking some aspect of its function.
This mutation occurs when the product can still interact with the same elements as the wild-type product but has a negative impact on its function.