Molecular Basis for Repressor Activity of Qβ Replicase

WITH the purification and characterization of viral replicases, a novel feature of nucleic acid polymerases—stringent template specificity—was recognized^1,2. Qβ replicase, the most extensively studied viral RNA polymerase^2–8, is now known to replicate Qβ RNA², the complementary Qβ minus strand⁹, RNA molecules described as “variants” of Qβ RNA^10,11 and a set of small RNAs of unknown origin which accumulate in Qβ-infected Escherichia coli, collectively designated as “6S RNA”¹². On the other hand, the RNA from phages related distantly, if at all, to Qβ^13,14, such as MS2 or R17 and of other viruses such as TMV² or AMV (Diggelmann and Weissmann, unpublished results) are completely inert as templates, as are ribosomal and tRNA from E. coli². Poly C and C-rich synthetic copolymers at high concentrations elicit synthesis which, however, remains restricted to the formation of a strand complementary to the template^15,16.     

Bulbing in Long-day Onion (Allium cepa L.) Cultured In Vitro: Comparison Between Sugar Feeding and Light Induction

Bulbs were obtained on onion plants cultured in vitro. No bulbinghappened under long days with fluorescent light and 30–40g l^–1 sucrose. Bulb formation was mainly dependent eitheron sucrose concentration in the culture medium, or on lightspectral composition. Raising the sucrose concentration from40 to 120 g l^–1 increased plant basal swelling and stoppedfurther vegetative development. These plants were not dormant.When fluorescent light was enriched in incandescence duringa long day period, bulbs were obtained in two months and underwenta consecutive dormancy. Bulb, dormancy, light spectral quality, photoperiod, R: FR ratio, sugar, tissue culture     

THE MORAL OBLIGATION TO CREATE CHILDREN WITH THE BEST CHANCE OF THE BEST LIFE

According to what we call the Principle of Procreative Beneficence (PB), couples who decide to have a child have a significant moral reason to select the child who, given his or her genetic endowment, can be expected to enjoy the most well-being. In the first part of this paper, we introduce PB, explain its content, grounds, and implications, and defend it against various objections. In the second part, we argue that PB is superior to competing principles of procreative selection such as that of procreative autonomy. In the third part of the paper, we consider the relation between PB and disability. We develop a revisionary account of disability, in which disability is a species of instrumental badness that is context- and person-relative. Although PB instructs us to aim to reduce disability in future children whenever possible, it does not privilege the normal. What matters is not whether future children meet certain biological or statistical norms, but what level of well-being they can be expected to have.