The mutation that occurs when a single nucleotide is altered in a DNA sequence is called a point mutation. Point mutations can involve changes such as substitutions, deletions, or insertions of nucleotides. These alterations can lead to various outcomes, including silent mutations, missense mutations, or nonsense mutations, potentially impacting protein synthesis and function. Understanding point mutations is crucial in molecular biology, genetics, and medicine, as they can lead to diseases or contribute to evolutionary processes.