A DNA sequence is a specific order of nucleotides in a DNA molecule. Nucleotides are the building blocks of DNA and consist of a sugar, a phosphate group, and a nitrogenous base. The sequence of these bases—adenine (A), thymine (T), cytosine (C), and guanine (G)—determines the genetic information carried by an organism. DNA sequences are crucial for various biological processes, including gene expression and replication. Scientists analyze these sequences to understand genetic traits, identify diseases, and study evolutionary relationships among different species. The complete set of DNA sequences in an organism is known as its genome.