  We propose a model for the elastic properties of RNA gels. The model predicts
anomalous elastic properties in the form of a negative Poisson ratio and shape
instabilities. The anomalous elasticity is generated by the non-Gaussian
force-deformation relation of single-stranded RNA. The effect is greatly
magnified by broken rotational symmetry produced by double-stranded sequences
and the concomitant soft modes of uniaxial elastomers.
