ONE SCIENCE

In this groundbreaking paper, Stanley B. Prusiner presents evidence that the causative agent of scrapie, a neurodegenerative disease in sheep and goats, is an infectious protein particle, which he calls a "prion." The resistance of the prion to procedures that modify nucleic acids, its heterogeneity in size and charge, and its partial purification are described. The hypothetical mechanisms of prion replication are discussed, considering the possibility that it lacks nucleic acid, and its possible involvement in other human neurodegenerative diseases is explored. The research proposes a new model for infectious agents, challenging the central dogma of molecular biology. Finally, the implications of understanding the structure and replication of prions for medicine are highlighted. Prusiner, S. B. (1982). Novel proteinaceous infectious particles cause scrapie. Science, 216(4542), 136-144.

Polymerase chain reaction (PCR) would not be the same without the discovery of Taq polymerase, a thermostable enzyme crucial for its efficiency and specificity. The steps of PCR (denaturation, hybridization, and extension) are explained, the effect of temperature on each step, and the advantages and limitations of Taq polymerase with other polymerases are compared. Finally, the various applications of PCR in different fields, including molecular biology, medicine and forensic science, are presented.

The paper presents Celera Genomics' work on human genome sequencing, detailing its methods, including shotgun sequencing and genome assembly. The process of building DNA libraries, data analysis, and assembly strategy is described, using two independent approaches. The paper also discusses gene prediction, identification of single nucleotide polymorphisms (SNPs), and a comparison with other eukaryotic genomes, highlighting expansions of human-specific protein families. Finally, an overview of the predicted genes and their involvement in complex biological processes is offered. Venter, J. C., Adams, M. D., Myers, E. W., Li, P. W., Mural, R. J., Sutton, G. G., ... & Waterston, R. H. (2001). The sequence of the human genome. Science, 291(5507), 1304-1351.

The sources analyze global contamination by PFAS, persistent chemicals that accumulate in the environment and pose a threat to human health and ecosystems. It is argued that the persistence of PFAS exceeds a new planetary limit, due to its levels in rainwater, soils and surface waters that exceed safety guidelines. Health impacts, such as immune suppression, are detailed and mitigation strategies are proposed, including restricting their use and developing safer alternatives. Finally, a timeline of key events related to the understanding and regulation of PFAS is presented. Cousins, I. T., Johansson, J. H., Salter, M. E., Sha, B., & Scheringer, M. (2022). Fuera del Espacio Operativo Seguro de un Nuevo Límite Planetario para Sustancias Per- y Polifluoroalquiladas (PFAS). Environmental Science & Technology, 56(15), 11172–11179. https://doi.org/10.1021/acs.est.2c02765

The text features excerpts from the first edition of Charles Darwin's On the Origin of Species. Darwin expounded his theory of natural selection, arguing that species evolve through the gradual accumulation of favorable variations. The laws of variation are discussed, including the influence of external conditions, the use and disuse of organs, and the correlation of growth. Sexual selection and the imperfection of the geological record are also discussed, presenting examples of species variability and difficulties in classification. Finally, Darwin addresses the geographical distribution of species and the importance of migration. Darwin, C. (1859). On the origin of species.

The article explores a new method for discovering new natural products from uncultivated soil microorganisms. It focuses on the concept of cloning the metagenome, that is, the set of genomes of the soil microflora, to access its biosynthetic machinery. This approach uses bacterial artificial chromosome (BAC) vectors to clone large fragments of DNA directly from the soil in E. coli, then the resulting clones are examined for biological activity. The authors argue that this technique overcomes the limitations of traditional farming methods and offers quick and efficient access to soil chemical diversity. Finally, the need for interdisciplinary collaboration between biologists and chemists to make the most of this potential is highlighted. Handelsman, J., Rondon, M. R., Brady, S. F., Clardy, J., & Goodman, R. M. (1998). Molecular biological access to the chemistry of unknown soil microbes: A new frontier for natural products. Chemistry & Biology, 5(10), R245-R249. https://doi.org/10.1016/S1074-5521(98)90108-9

The first paper, "A Novel Virus Isolated from the Human Respiratory Tract," describes the isolation of a new virus, called 229E, from samples taken from medical students with mild respiratory illness. The researchers showed that the virus is RNA, ether-sensitive, and not genetically related to known respiratory viruses. The second paper, "Non-Specific Hemadsorption by Rhesus Monkey Kidney Cells," examines the hemadsorption observed in rhesus monkey kidney cell cultures, a phenomenon commonly attributed to simian virus contamination. The authors argue that hemadsorption can be easily identified and differentiated from viral infection, and provides detailed information on this phenomenon in the context of virus detection in cell cultures. Hamre, D., & Procknow, J. J. (1966). A New Virus Isolated from the Human Respiratory Tract. Proceedings of the Society for Experimental Biology and Medicine, 121(1), 190–193. https://doi.org/10.3181/00379727-121-30734 Liu, Y.-C., Kuo, R.-L., & Shih, S.-R. (2020). COVID-19: The first documented coronavirus pandemic in history. Biomedical Journal, 43, 151-158. https://doi.org/10.1016/j.bj.2020.04.007

This scientific paper describes the sequencing, assembly, and genome analysis of the Mexican axolotl (Ambystoma mexicanum), a species of salamander known for its ability to regenerate. The researchers found that the axolotl genome is ten times larger than the human genome, mainly due to the expansion of long-termination repeat (LTR) retroelements. In addition, they found that the Pax3 gene, which is essential for tissue development in other vertebrates, is absent from the axolotl genome. Through gene-editing experiments, they showed that the axolotl's Pax7 gene has taken over the functions of Pax3. The article provides a valuable source of information for understanding genome evolution, regeneration mechanisms, and developmental processes in axolotls. Nowoshilow, S., Schloissnig, S., Fei, J.-F. et al. El genoma del ajolote y la evolución de los reguladores clave de la ormación de tejidos. Nature 554, 50–57 (2018). https://doi.org/10.1038/nature25458

This research paper, published in the journal Proceedings of the National Academy of Sciences, challenges the common belief that mitochondrial DNA (mtDNA) is inherited exclusively from the mother. The authors identified three unrelated families with unusually high levels of mtDNA heteroplasmy, suggesting transmission of mtDNA from both the father and mother. This finding has significant implications for our understanding of mitochondrial inheritance and opens up new avenues for the treatment of mitochondrial diseases. Luo, S., Valencia, C. A., Zhang, J., Lee, N.-C., Slone, J., Gui, B., Wang, X., Li, Z., Della, S., Brown, J., Chen, S. M., Chien, Y.-H., Hwu, W.-L., Fan, P.-C., Wong, L.-J., Atwal, P. S., & Huang, T. (2018). Biparental inheritance of mitochondrial DNA in humans. Proceedings of the National Academy of Sciences, 115(46), 11684–11689. https://doi.org/10.1073/pnas.1810946115

This scientific paper by Lynn Sagan, published in 1967, proposes a theory on the origin of eukaryotic cells, the "higher" cells that divide by classical mitosis. The theory argues that three fundamental organelles, mitochondria, photosynthetic plastids, and the basal bodies (9+2) of flagella, were originally free-living prokaryotic cells. Sagan describes the evolution of photosynthesis under anaerobic conditions in the early atmosphere, giving rise to anaerobic bacteria, photosynthetic bacteria, and finally to cyanophyte algae (and protoplasts). Subsequently, the evolution of aerobic metabolism in prokaryotes would have given rise to aerobic bacteria (protoflagella and promitochondria), presumably during the transition to an oxidizing atmosphere. Classical mitosis would have evolved in protozoan-like cells millions of years after the evolution of photosynthesis. Sagan presents a plausible scheme for the origin of classical mitosis in early amoeboflagellates, and how during the evolution of mitosis, some of these protozoans acquired photosynthetic plastids (derived from prokaryotes) symbiotically, giving rise to eukaryotic algae and green plants. The paper provides cytological, biochemical, and paleontological evidence for this theory, together with suggestions for its possible experimental verification, and discusses the implications of this theory for the systematics of lower organisms. Sagan, L. (1967). On the origin of mitosing cells. Journal of Theoretical Biology, 14, 225–274.