Describe a specific, real world example of a gene mutation that resulted in a harmful, beneficial, and/or neutral effect.

Harmful mutations may cause genetic disorders or cancer. A genetic disorder is a disease caused by a mutation in one or a few genes. A human example is cystic fibrosis. A mutation in a single gene causes the body to produce thick, sticky mucus that clogs the lungs and blocks ducts in digestive organs.
There are several well-known examples of beneficial mutations. Here are two such examples: Mutations have occurred in bacteria that allow the bacteria to survive in the presence of antibiotic drugs, leading to the evolution of antibiotic-resistant strains of bacteria.
In fact, the G-T mutation is the single most common mutation in human DNA. It occurs about once in every 10,000 to 100,000 base pairs -- which doesn't sound like a lot, until you consider that the human genome contains 3 billion base pairs.

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