Question

Describe how a mutation may have a negative, positive, or neutral impact on phenotype

Answer 1

Some mutations don't have any noticeable effect on the phenotype of an organism. This can happen in many situations: perhaps the mutation occurs in a stretch of DNA with no function, or perhaps the mutation occurs in a protein-coding region but ends up not affecting the amino acid sequence of the protein.
Some really important phenotypic changes, like DDT resistance in insects, are sometimes caused by single mutations. A single mutation can also have strong negative effects on the organism. Mutations that cause the death of an organism are called lethal — and it doesn't get more negative than that.

Mutations in many bacteria that allow them to survive in the presence of antibiotic drugs. The mutations lead to antibiotic-resistant strains of bacteria. A unique mutation is found in people in a small town in Italy. The mutation protects them from developing atherosclerosis, which is the dangerous buildup of fatty materials in blood vessels. The individual in which the mutation first appeared has even been identified.

Cancer is a disease in which cells grow out of control and form abnormal masses of cells. It is generally caused by mutations in genes that regulate the cell cycle. Because of the mutations, cells with damaged DNA are allowed to divide without limits. Cancer genes can be inherited.