Final answer:
A mutation is a random change in the nucleotide sequence that affects an organism's genotype. These changes can be spontaneous or induced by external factors, and while most do not impact the organism, some can lead to significant changes in protein function.
Step-by-step explanation:
A mutation is a random change in the nucleotide sequence that alters the genotype of an organism. These changes can sometimes lead to a different amino acid sequence in proteins, which may affect an organism's phenotype. Mutations may occur spontaneously due to errors in DNA replication or be induced by external factors such as radiation, chemicals, or viruses. Genetic diversity arises from such mutations, which are essential for evolution, though most mutations do not have an effect on the organism. Certain mutations, known as frameshift mutations, result from the insertion or deletion of nucleotides that shift the reading frame of the genetic code, which can have significant implications for protein function.