What is the effect of a mutation in a gene?

The effect of a mutation in a gene is often associated with its potential to alter the function of the protein produced by that gene. Mutations can lead to changes in the amino acid sequence of a protein, which may affect its shape and function. Depending on the nature and location of the mutation, the resulting protein may be more active, less active, or entirely nonfunctional. This variability can have diverse implications for the organism, ranging from no observable effect to significant physiological changes.

Mutations play a critical role in evolution and genetic diversity, as they can introduce new traits within a population. While some mutations may confer advantages or disadvantages, the key point is that they influence the protein's function, which can cascade into various outcomes based on environmental pressures and interactions within the organism. Thus, option B captures the essence of how mutations can impact gene expression and functionality.