1. The structure formed by a polynucleic acid by base-pairing between neighboring complementary sequences of a single strand of either DNA or RNA. 2. The structure seen in a prostaglandin where two segments of the molecule fold back on one another.
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hair·pin 'ha(ə)r-.pin, 'he(ə)r- n a region in single-stranded RNA or DNA that is double-stranded due to pairing between purine and pyrimidine bases in adjacent sequences of the RNA or DNA that are complementary and inverted called also hairpin loop
Medical dictionary. 2011.