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Integration and Excision of DNA Molecules
The topic of this years' ~osbach Colloquium was DNA integration. We have tried to bring together experts from different fields of research who are studying natural processes by which DNA molecules from differ ent sources are linked. It has been known for a long time that such linkage occurs between the chromosomes of bacteriophages and plasmids on the one hand and the chromosome of the bacterial host on the other. This process has been especially well studied in bacteriophage A. Since it is controlled in a complicated way, we began with a lecture by M. ptashne on these regulatory processes. H. Nash described the inte gration of bacteriophage A into the bacterial chromosome. To put this site-specific process into perspective, G. Mosig lectured on genetic recombination in prokaryotes in general and K. Murray described the use of bacteriophage A as an artificial vector for genetic engineering. A different kind of bacteriophage integration is shown by bacteriophage Mu, which is much less specific in its choice of an integration site than A. The properties of this phage were described by P. van de Putte.
Current Topics in Microbiology and Immunology
Influenza continues to be one of the major epidemic diseases of man and is, in fact, his only remaining pandemic disease (BEVERIDGE, 1969). This is largely because influenza virus undergoes extreme antigenic variation, the mechanism of which is still poorly understood. Two kinds of antigenic variation occur in influenza viruses, antigenic drift and major antigenic shifts; both involve chan ges in the hemagglutinin and neuraminidase antigens on the surface of the virus. Antigenic drift, which involves gradual changes in the surface antigens of influenza virus, is thought to result from the selection by an immune popula tion of mutant virus particles with altered antigenic determinants. These mutants therefore possess a growth advantage in the presence of antibody (FRAN CIS and MAASSAB, 1965; ARCHETTI and HORSFALL, 1950; HAMRE et aI., 1958). It has been shown that antigenic mutants isolated in vitro by selection with antibody have changes in amino acid sequence in the polypeptides of the hem agglutinin subunits (LAVER and WEBSTER, 1968) and it is likely that antigenic drift in the neuraminidase occurs by the same mechanism.
Current Topics in Microbiology and Immunology / Ergebnisse der Mikrobiologie und Immunitätsforschung
The processes involved in herpesvirus replication, latency, and oncogenic transformation, have, in general, been rather poorly defined. A primary reason for this is the size and complexity of the herpesvirus genome. Undoubtedly, a better understanding of the functions of the viral genome in infected and transformed cells will be achieved through studies with temperature-sensitive (ts) mutants of herpesviruses since, theoretically, any essential gene function can be affected by mutants of this type. A. The Herpesviruses A consideration of the genetic analysis of members of the herpesvirus group necessitates a description, albeit brief, of the properties of the group and, most importantly, of ...
