STRUCTURAL MECHANICS OF BENT DNA

The DNA molecule is a familiar object. It is often depicted in magazin es and advertisements as a double helix, with the letters of the genet ic code strung along the two spiral backbones and joined together in p airs. In such pictures the molecule is usually shown as straight; yet in the chromosomes of living organisms, DNA is curved and wound up int o condensed packages. This article explains what is involved in such b ending of DNA in the cell. It uses the ideas of structural mechanics - a tool of engineers - to show how the various components fit together when the molecule is bent.