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Strand
DNA is a molecule formed by a two strands (chains) coiled around each other, 2nm in diameter. Thus DNA takes the form of a “double helix”. These antiparallel strands (taking opposing directions) wind around each other like the threads of a screw, and are joined by “bonds”.
Since the genetic information is duplicated on each of the two strands, a damaged strand can be repaired by a corresponding strand that has remained intact. However, defective repair or the failure to repair a damaged strand leads to the death of the cell or to rearrangements liable to cause cancers.