Why does mutations may or may not affect the expression of a gene?

Mutations can affect gene expression by altering the DNA sequence in a way that changes how the gene is transcribed or translated, potentially leading to a dysfunctional protein or no protein at all. However, not all mutations have significant effects; some may occur in non-coding regions, be silent (not changing the amino acid sequence), or be compensated by other cellular mechanisms. Additionally, the impact of a mutation can depend on environmental factors and the presence of regulatory elements. Thus, the consequences of mutations on gene expression can vary widely.