A Chromosome Has Received Two Double-Stranded Breaks

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The Answer is If the two breaks occur on the same chromosome arm, there are two possibilities. First an interstitial deletion can result, after the central piece is excised and the two ends are fused at the breakpoints (the excised central fragment cannot be propagated because it lacks a centromere). Alternatively, a paracentric inversion results (the central piece, lacking a centromere, rotates and then is fused to the end pieces).
If the two breaks occur on different chromosome arms, deletion is not normally viable: the central fragment cannot be excised and lost as it contains the centromere. Instead, there are two viable alternatives. First, a pericentric inversion results (the central piece, containing a centromere, rotates and then is fused to the end pieces). More rarely, a ring chromosome can occur where the two ends of the central fragment fuse to form a circular chromosome.

A Chromosome Has Received Two Double-Stranded Breaks

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