Molecular Biology
Promoter (Genetics)
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A DNA sequence where RNA polymerase binds to begin transcription. Promoters control when, where, and how strongly genes are expressed—the 'if-then' logic of the genome.
Biological Context
Promoters are DNA sequences upstream of genes where transcription machinery (RNA polymerase) binds. Different promoter sequences respond to different signals—heat shock, nutrient availability, hormones, developmental cues. Promoter strength determines expression level (how much protein is made). Mutations in promoters can cause disease by inappropriate activation or silencing of genes. Cancer often involves promoter dysfunction.