Date of Birth: 06/03/1929
Place of birth: granichen
In 1953, Alexander enrolled at the University of Geneva, graduate school and became a senior laboratory assistant at the Department of Biophysics. Here he developed methods for studying bacteriophages (viruses that infect bacteria) using electron microscopy - method of research, allows us to study the microstructure of cells and tissues using electron beam. As a graduate student, Alexander presented an analysis of the model of deoxyribonucleic acid (DNA), developed by James Watson and Francis Crick, a discussion club at the department, whose members are engaged in a discussion of those discoveries, which learned from scientific journals. It was the beginning of long-term interest to A. physiology and genetics of bacteriophages.
As already mentioned, bacteriophages - are viruses that infect bacterial cells. They belong to the most primitive forms of life and consist of a core formed by nucleic acids, and the outer protein shell. After the introduction of the phage to the bacterial cell are three possible ways of its further development. Firstly, it can disrupt the regulation of cell biochemical system, begin to multiply and cause its destruction with the release of new phage particles. Secondly, the phage DNA can be incorporated into a bacterial cell (in this case it will be called prophage) and during fission, like a gene of the cell, be transmitted to daughter cells. Finally, the phage may be digested by enzymes of the bacterial cell; now it is called "modification, controlled by the host cell."
In the early 50-ies., When Alexander was still a student, the first electron micrographs of bacteriophages were obtained at the Department of Biophysics, University of Geneva. In 1958, Alexander received at this university doctorate with a thesis devoted to the defects of the mutant strain of bacteriophage & # 955 ;, and then for two years as a postdoctoral fellow and research associate at the Department of Microbiology of the University of Southern California. In 1960, Alexander returned to the University of Geneva, but first visited a number of American laboratories involved in the study of bacteriophages. A. In the United States not only has mastered the newest methods of genetics of bacteria and bacteriophages research, but also interested in the phenomenon of "limitations caused by a host cell", or by restriction. With the support of the Swiss National Science Foundation, A. engaged in the molecular basis of the restriction of bacteriophages.
In 1962, together with the employee-doctoral A. revealed the mechanism of "limitations caused by a host cell", or restriction-modification. In this process the phage DNA is cleaved into fragments by the action of a restriction endonuclease enzyme, acting in conjunction with the methylase. Thus bacterial endonuclease recognizes a specific sequence of nucleotides in DNA and bakteriofagalnoy respective portions cleaves the DNA, thereby inactivating it. Methylase recognizes the same DNA sequence in the bacterial cell, it methylates and therefore protects against enzymatic degradation private endonuclease (methylation - joining the DNA is a methyl group, consisting of one carbon atom and three hydrogen atoms).
Alexander called this system of two enzymes of restriction-modification system. Together with his team he was not only isolated and purified endonuclease and methylase (these enzymes respectively limit, ie suppress the replication of bacteriophage DNA and alter the DNA of the host cell), but also found bacteria-mutants in which both were defective enzyme. A similar call restriction endonuclease isolated from E. coli Escherihia coli, endonuclease type I. Such endonucleases recognize specific though bakteriofagalnoy DNA nucleotides, cleaved at its most different sites. A. predicted that there must be type II of the endonuclease, acting exactly on the site that they recognize that they will allow for an accurate analysis of genetic structure of DNA, and that such a splitting of genes ever will be the usual method. All of these predictions have come true.
In 1965, Alexander became an associate professor of Molecular Biology, University of Geneva. he married a year later. In A. and his wife, two daughters, Antonia. In the late 60-ies. A. dissatisfied with the fact that the students became interested not so much a science as politics, retired from the University of Geneva, and accepted the offer to become a professor of Biology center - a new research institute, created at the University of Basel. A. Here, for wide open research opportunities. In 1970 ... 1971. Until the equipment was installed, A. worked as a visiting researcher at the Department of Molecular Biology, University of California at Berkeley. On his return to Switzerland AG became Professor of Molecular Biology, University of Basel.
In 1978, A. together with Daniel Nathans and Hamilton Smith, Nobel Prize in Physiology or Medicine was awarded "for the discovery of restriction enzymes and their application in molecular genetics." In his welcoming speech, a scientist at the Karolinska Institute, Peter Reichardt noted the contribution of A. in the discovery of restriction enzymes. He said that "in a series of simple but elegant experiments, A. showed that the controlled modification of the host cell due to the changes in DNA and, obviously, is to protect the host cell from foreign genes." "The use of restriction enzymes, - he continued - has revolutionized the genetics of higher organisms and completely changed our ideas about the organization of their genes. It was found that in contrast to DNA of bacteria of DNA in higher organisms - is not a continuous sequence encoding a protein: genes are "neutral" areas alternating with areas that store the genetic code. "
Continuing his studies at the University of Basel, Alexander became interested in different types of gene systems, recombination and gene diversification. Today we know that the elements of the genes and the genes themselves are mobile and can be exchanged between the different gene systems. Thus, they may "embed" in DNA by recombination method, and can carry from one DNA molecule to another. A. suggested. diversification of the genetic code that bacteria in the course of evolution can be explained by gene exchange.
A wonderful family man, A. considers himself a happy man, because I always feel the support of his wife and two daughters. And he answered trying to surround them with care, without which there can not be a harmonious family life.