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Illustration of a helicase enzyme separating two strands of deoxyribonucleic acid (DNA). The process of unraveling a double helix of nucleic acid strands is important to many cellular functions, such as DNA replication, RNA synthesis, RNA transcription, DNA recombination, and DNA repair.
Illustration of DNA testing results, showing how a single strand of DNA (top) can be analyzed and used as evidence in a criminal case. DNA is extracted from a sample and treated, and the pattern is transferred to a nylon sheet (bottom left). Analysis can compare DNA from a crime scene to a sample from a suspect, as shown in the patterns at right.
DNA replication initiation by an enzyme in a prokaryote (E. coli), based on a Kornberg model. The dnaA protein enzyme binds to DNA at the replication origin in a core complex (upper left), beginning the "melting," or opening, of the DNA double strand. Not shown, the helicase enzyme, dnaB, loaded in a complex with dnaC, will then continue unzipping the DNA.