We introduce the concept of an analog neural network represented by chemica
l operations performed on strands of DNA. This new type of DNA computing ha
s the advantage that it should be fault tolerant and thus more immune to DN
A hybridization errors than a Boolean DNA computer. We describe a particula
r set of DNA operations to effect the interconversion of electrical and DNA
data and to represent the Hopfield associative memory and the feed-forward
neural network of Rumelhart et al. We speculate that networks containing a
s many as 10(9) neurons might be feasible. (C) 1999 Elsevier Science Irelan
d Ltd. All rights reserved.