The microarchitecture of DNA replication domains

Most DNA synthesis in HeLa cell nucleus is concentrated in discrete foci. These synthetic sites can be identified by electron microscopy after allowing permeabilized cells to elongate nascent DNA in the presence of biotin-dUTP. Biotin incorporated into nascent DNA can be then immunolabeled with gold particles. Two types of DNA synthetic sites/replication factories can be distinguished at ultrastructural level: (1) electron-dense structures—replication bodies (RB), and (2) focal replication sites with no distinct underlying structure—replication foci (RF). The protein composition of these synthetic sites was studied using double immunogold labeling. We have found that both structures contain (a) proteins involved in DNA replication (DNA polymerase α, PCNA), (b) regulators of the cell cycle (cyclin A, cdk2), and (c) RNA processing components like Sm and SS-B/La auto antigens, p80-coilin, hnRNPs A1 and C1/C2. However, at least four regulatory and structural proteins (Cdk1, cyclin B1, PML and lamin B1) differ in their presence in RB and RF. Moreover, in contrast to RF, RB have structural organization. For example, while DNA polymerase α, PCNA and hnRNP A1 were diffusely spread throughout RB, hnRNP C1/C2 was found only at the very outside. Surprisingly, RB contained only small amounts of DNA. In conclusion, synthetic sites of both types contain similar but not the same sets of proteins. RB, however, have more developed microarchitecture, apparently with specific functional zones. This data suggest possible differences in genome regions replicated by these two types of replication factories.     

Some connections between physiognomic traits and intelligence

A sample of 84 female subjects (students) was taken and split up on the basis of the IST-ratings (“Intelligence Structure Test” by Amthauer) into two extreme groups of “more intelligent” (N = 14) and “less intelligent” (N = 11) subjects with an aim to testing Kozeny's findings. Using his photographic-statistical method, Kozeny had observed that “more intelligent” people have a more open eye, a smaller and straighter mouth, a stronger chin, and—above all in its side dimensions—a better developed forehead. These physiognomic indicators of differences in intelligence were confirmed to a large extent by the measurements taken from the portraits of the subjects.     

Parsimony Analysis as a Specific Kind of Homology Estimation and the Implications for Character Weighting

“Remane-Hennigian systematists” still reject parsimony analysis for phylogenetics, because homology or apomorphy analyses are not included. In contrast, “pattern cladists” regard homology as a deductive concept after applying a parsimony test of character congruence. However, as in molecular phylogeny, selection of “good” characters is always done on the basis of ana priorihomology analysis. The distribution criterion of homology—“homologous characters have identical or hierarchical distribution”—is the basis of parsimony analysis. Because this criterion also might fail in cases of genealogical reticulation or concerted homoplasy, character congruence is not a strict test but another probabilistic criterion of homology. A synthetic approach is proposed for phenotypic analysis with application ofa prioricriteria of homology. The resultinga prioriprobabilities of homology serve as criteria for selection and weighting of characters (very low = not selected/poor/mediocre/good/Dollo characters). After application of a parsimony algorithm the final cladogram decides homology estimations.     

The RNA World on Ice: A New Scenario for the Emergence of RNA Information

The RNA world hypothesis refers to a hypothetical era prior to coded peptide synthesis, where RNA was the major structural, genetic, and catalytic agent. Though it is a widely accepted scenario, a number of vexing difficulties remain. In this review we focus on a missing link of the RNA world hypothesis—primitive miniribozymes, in particular ligases, and discuss the role of these molecules in the evolution of RNA size and complexity. We argue that prebiotic conditions associated with freezing, rather than “warm and wet” conditions, could have been of key importance in the early RNA world.[Reviewing Editor: Dr. Niles Lehman]