From a biological motivation of interactions between linear and circular DNA sequences, we propose a new type of splicing models called circular H systems and show that they have the same computational power as Turing machines. It is also shown that there effectively exists a universal circular H system which can simulate any circular H system with the same terminal alphabet, which strongly suggests a feasible design for a DNA computer based on circular splicing. 1 Introduction Since Adleman's breath-taking paper on molecular (DNA) computing ([1]), there have already been quite a few papers on this challenging topic : [10] shows how to solve NP-complete problems using DNA, while [3] discusses a design method for simulating a Turing machine by molecular biological techniques and shows how to compute PSPACE, and [4]) gives a methodology for breaking the DES using techniques in genetic engineering. In response to the rapid stream of experimental research on this new computation paradigm...

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How do cells and nature "compute"? They read and "rewrite" DNA all the time, by processes that modify sequences at the DNA or RNA level. In 1994, Adleman's elegant solution to a seven-city Directed Hamiltonian Path problem using DNA [1] launched the new field of DNA computing, which in a few years has grown to international scope. However, unknown to this field, ciliated protozoans of genus Oxytricha and Stylonychia had solved a potentially harder problem using DNA several million years earlier. The solution to this "problem", which occurs during the process of gene unscrambling, represents one of nature's ingenious solutions to the problem of the creation of genes. Here we develop a model for the guided homologous recombinations that take place during gene rearrangement and prove that such a model has the computational power of a Turing machine, the accepted formal model of computation. This indicates that, in principle, these unicellular organisms may have the capacity to perform at ...

Biological macromolecules can be viewed, at one level, as strings of symbols. Collections of such molecules can thus be considered to be sets of strings, i.e. formal languages. This article reviews languagetheoretic approaches to describing intramolecular and intermolecular structural interactions within these molecules, and evolutionary relationships between them. 1 Introduction The author has for some time been investigating the application of formal language theory to biological macromolecules, primarily nucleic acids because of the relative simplicity of the biochemical structures and interactions. After introducing the very simple mathematical foundations for these investigations, this article will review three major lines of research. These can largely be found in more fully developed form in referenced publications, though some new material is also included in each case. The sections below will deal with the use of formal grammars to describe intramolecular interactions [17, 18...

In [8] we proposed a model to describe the homologous recombinations that take place during massive gene rearrangements in hypotrichous ciliates. Here we develop the model by introducing the dependency of homologous recombinations on the presence of certain contexts. We then prove that such a model has the computational power of a Turing machine. This indicates that, in principle, some unicellular organisms may have the capacity to perform any computation carried out by an electronic computer.

This paper concerns an efficient algorithm for learning in the limit a special type of regular languages called locally testable languages from positive data, and its application to identifying the protein ff-chain region in amino acid sequences. First, we present a linear time algorithm that, given a locally testable language, learns (identifies) its deterministic finite state automaton in the limit from only positive data. This provides us with a practical and efficient learning method for a specific domain of symbolic analysis. We then describe several experimental results using the learning algorithm developed above. Following a theoretical observation which strongly suggests that a certain type of amino acid sequences can be expressed by a locally testable language, we apply the learning algorithm to identifying the protein ff-chain region in amino acid sequences for hemoglobin. Experimental scores show an overall success rate of 95 % correct identification for positive data, an...

This article arose from a reading of the paper of Q.Ouyang, P.D.Kaplan, S.Liu and A.Libchaber

In search for a universal splicing system, in this paper we present a Post system universal for the class of Post systems, and we discuss its translation into an extended splicing system with multiplicity. We also discuss the complexity of the resulting universal splicing system, comparing our result with recent known results about the translation of universal Turing machines into splicing systems. 1 Introduction Since the possibility of molecular computing was shown by Adleman's pioneering work ([1]) which, in a test tube, experimentally solves a small instance of an NPcomplete problem, the theoretical formalization of such a new computing technology has been attracting much attention in computer science ([3][5][6][12][17]). One of the formal frameworks for molecular computations is the Tom Head's splicing system ( or H system ), which gives a theoretical foundation for computing based on DNA recombination. Tom Head's seminal work ([9]) on modeling DNA recombination as a splicing sys...

We prove that a reversible model for the guided homologous recombinations that take place during gene rearrangement in ciliates has the computational power of a Turing machine, the accepted formal model of computation. This indicates that, in principle, these unicellular organisms may have the capacity to perform any computation carried out by an electronic computer.

. DNA splicing systems (or simply splicing systems) are a new type of generative mechanisms for modeling DNA recombination behaviors, initiated by Tom Head's seminal paper ([8]). For this reason, splicing systems are sometimes called Head systems (H systems), and a number of extensive work on this exciting subject have already been reported by many authors. Among others, Paun's recent result shows that extended H systems with finite sets of axioms and regular sets of rules exactly characterize the recursively enumerable languages, thus having the full power of Turing machines ([13]). Also, more recently it is shown that there is a universal extended H system analogous to a universal Turing machine ([4]). This paper concerns further formal study on the generative powers of extended H systems. First, using a classical result by Post which characterizes the recursively enumerable languages in terms of his Post Normal systems, we establish several new characterizations of exten...