The Historical Contributions Of Francis Crick On Genetic Code Research

F.H.C.Crick (1916-2004) is one of the most distinguished scientists inthe history of science. He changed his major from physics to biology. Hisresearch interests arranged many fields of biology such as cytoplasm, protein,DNA, genetic code and human consciousness, etc..Based on a careful examination of Crick’s original academic papers ongenetic code and related study literature, the present dissertation deals withthe essential contents of his theories by means of the methods of literature andconcept analysis.The ultimate goal of the dissertation is to give a historicalimage of his scientific work.Specifically, the achievements of Crick on the study of genetic codetheory are presented according to the first hand materials including CrickCrick’s original academic papers and some related study literature. Theevolution of concepts and hypotheses raised by him is investigated, so is histhinking effect on modern code field. All the concentrated problems areillustrated. By using the case study method, the essential contents ofMutational Deterioration theory are reviewed, and the truth is that Crick’simportant views of wobble hypothesis and frozen accident have greatinfluence on Mutational Deterioration theory.The dissertation is divided into the six chapters. The first chapter is about the study of Crick’s lifetime. His personal academic options and the mainachievements have been analyzed completely. The important contributions inhis research fields have been summarized briefly. All of these prove that hislifetime is prudent, constant and intelligent. Among his academic activities,genetic code is recognized as the most important part. The study on geneticcode is on the basis of the integration of physics thinking with biology objects.The integration is an effective attempt of his original ideal involved inbiophysics.The early development of genetic code is reviewed in the second chapter.The historical evolution of the concept "genetic material" is introduced，theorigin of the study of genetic code is made clear, and moreover, the point isthat four early code rudiments are proposed. Embryologists J.Brachet firstlaunched the research related to information flow from DNA to protein,biologists A.L.Dounce first put forward the coding assumption, and physicistsG.Gamow attached importance to the coding problem at first in detail.By theinspiriting of the work of Gamow, Crick stepped into the road of studyinggenetic code, bringing forth a series of coding schemes and struggling withdifficulty in the beginning of research. The hard work embodies his scientificspirit such as perseverance and innovation.The third chapter is to trace back to the reasons why Crick could giverise to the thoughts about genetic code. The whole psychological process ofCrick is probed through referring to his papers, books and personal communication letters. The dissertation comes to the conclusion that threeimportant factors contribute to his interests in the study of genetic code. First,it is from Darwinism. Second, Crick has the ability to gain an insight into thenew things and benefits from his physics thinking. Third, he has committedhis full devotion to science.Both the fourth and the fifth chapters are the main parts of the wholepaper. The research work of Crick on the genetic code is divided into twoparts. The first includes his fundamentals, and the second is made of thesyntheses. In the fourth chapter, his fundamentals including coding problem，protein synthesis and triplet are probed. Coding problem is the most essentialissue in his study. Based on the historical study and concept analyzing ofCrick on coding problem, it is believed that although the first person who putforward to coding problem was not Crick, he was aware of the importance ofthe issue firstly. With a lot of thinking and theory analyses, Crick appliedhimself to that problem. At a low ebb of the coding research, he built up thetheory frame, making proposition of "sequence synthesis" and "centraldogma". The performance shows the value of his hypothesis and historicallessons that experience comes from mistakes. The research of Crick in theaspect proves the scientific logic that the academic research should conformto the way from easy to difficult and seeking evidences. Sequentially, hedevised an original experiment that proved the essence of code is triplet. Thesuccessful experiment plays an important role in history of code discovery and also serves as a link between the past and the future. It is the first timethat the essence of genetic code was expanded and helped him further tobecome a theoretician rooted in experiments.The fifth chapter is to do some synthesis research of Crick on geneticcode from the perspective of internal history. The research of Crick involvedin the properties of genetic code, wobble hypothesis, stop codons, theconstruction of the standard code table and the origin and evolution of code isintegrated completely in the chapter. Contributions of Crick and otherscientists to the syntheses process of the theory of genetic code andconstruction of the code table are shown by explaining his five timessyntheses. Based on two-level researches of Crick，the author thinks that themain characteristics of his researches in the aspect are as follows: generality,systematicness, logicality and essentiality; frame research style; boldassumptions and innovation; thinking rooted in history and experiments.These characteristics show the influence of the strong foundation of physicsknowledge and physics thinking to him in his scientific activities on geneticcode.The impact of the research of Crick in the field of genetic code is studiedprimarily in the chapter6. Some concentrated problems, such as thedegeneracy of genetic code and deviant code, redefinition of nonsense codons,the expanding of code, the origin and evolution of code, etc, are analyzed atfirst. And then, through a case study on Mutation Deterioration theory proposed by Chinese scholar, the historical background and the essentialcontent of the theory of genetic code is examined. Mutation deteriorationtheory may date back to1980s. From the rationality of underlyingassumptions, the clarity of the logical structure, the completeness and theuniversality of interpretation of experimental data, the theory is particularlysuccessful among many other theories on the code origin and evolution. Thefact that the code study of Crick has direct effects on the MutationDeterioration theory is demonstrated in detail for the first time.