Two mice have different parents. They both have the same protein for whisker thickness in their cells.

Due to presence of similar protein.

Explanation:

The two mice are different from one another due to their different parents so in that way the physical features of both mice are different from one another. Both mice have the same protein for whisker thickness in their cells that leads to same whisker in both mice. The common feature in both mice are the protein that is responsible for whisker thickness so both have same whisker on their face.