Hairpin

A hairpin is a blunt needle? to fixate hair? into position.

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In genetics, a hairpin is a part of single-stranded DNA, usually a palindromic sequence, that aligns with itself to form a needle-like structure. A single-stranded DNA like

 ---CCTGCXXXXXXXGCAGG---

becomes

 ---C G---
    C G
    T A
    G C
    C G
    X X
   X   X
    X X
     X