Selectivity Advantages

Infection prevented Protection from CPE Protection from CTL Selective advantage... 

Infection is established Viral genes expressed Viral genome replicated Production of infectious virions blocked No protection from CPE No protection from CTL No selective advantage... 

Two clinical studies with CD4+ lymphocytes expressing an antiviral were performed. Marking in both studies was low but there was some indication for a possible selective advantage conferred by the ribozyme (Buchschacher and Wong-Staal 2001 Macpherson et al. 2005). 

Schwartz, D. (1969). An example of gene fixation resulting from selective advantage in suboptimal conditions. American Naturalist, 103, 479-81. 

Figure 38-10. Picornavimses disrupt the 4F complex. The 4E-4G complex (4F) directs the 40S ribosomal subunit to the typical capped mRNA (see text). 4G alone is sufficient for targeting the 40S subunit to the internal ribosomal entry site (IRES) of viral mRNAs. To gain selective advantage, certain viruses (eg, poliovirus) have a protease that cleaves the 4E binding site from the amino terminal end of 4G. This truncated 4G can direct the 40S ribosomal subunit to mRNAs that have an IRES but not to those that have a cap. The widths of the arrows indicate the rate of translation initiation from the AUG codon in each example.

The clinical relevance of biocide resistance of antibiotic-resistant staphylococci is, however, unclear. It has been claimed that the resistance of these organisms to cationic-type biocides confers a selective advantage, i.e. survival, when such disinfectants are employed clinically. However, the in-use concentrations are several times higher than those to which the organisms are resistant. 

M. Eigen describes this process roughly as follows let us consider a self-replicating system which is characterized by a quantity of information equal to N bits. The probability that a bit is incorrectly copied is w, and the selection reacts to errors by means of a selection factor S. In other words an error-free system has a selection advantage S over a system with an error. The survival criterion is then ... 

If the above condition is fulfilled, the selection advantage of the error-free system is so large that a number of errors in the total population can be tolerated. 

The growth-associated synthesis of poly(3HB) is clearly of selective advantage. The synthesis of poly(3HB) is not only - as stated above - an investment in the future, but also an opportunity to cope with and widen actually existing intrinsic bottlenecks. 

---