Reconstructing the Deep Population History of Central and South America

We report genome-wide ancient DNA from 49 individuals forming four parallel time transects in Belize, Brazil, the Central Andes, and the Southern Cone, each dating to at least 9,000 years ago. The common ancestral population radiated rapidly from just one of the two early branches that contributed to Native Americans today. We document two previously unappreciated streams of gene flow between North and South America. One affected the Central Andes by 4,200 years ago, while the other explains an affinity between the oldest North American genome associated with the Clovis culture and the oldest Central and South Americans from Chile, Brazil, and Belize. However, this was not the primary source for later South Americans, as the other ancient individuals derive from lineages without specific affinity to the Clovis-associated genome, suggesting a population replacement that began at least 9,000 years ago and was followed by substantial population continuity in multiple regions

Incomplete penetrance in maize genotypes segregating for the polyembryony trait

To study the genetic control of polyembryony trait in maize germplasm a series of experiments were carried out.The genetic material came from crossings among two polyembryonic populations and 16 different genotypes,normal type maize. A total of 27 F1 were generated in 2016, and from those, there were derived 22 F2, and 20backcrosses genotypes. The experiments were carried out in two locations in Northern Mexico. Several genotypesin the second generation progenies share the same preceding F1. The theoretical expectations for polyembryony(PEm, in short) proportions in F2 and backcrossing are 0.0625 and 0.25, respectively. It is instructive to statethat given the PEm recessiveness, all the F1 genotypes were normal type plants: one seedling per germinatedseed. The statistical methods applied to the experimental data were the exact Binomial test, for the segregatingproportions in F2, and the exact Fisher test to prove for independence between environments and the PEm genotypes.There were used R procedures for calculations. Based on the results, we have concluded that 1) varyinggenetic backgrounds in crossings might have an impact on the trait segregation proportions depending upon thespecific parents’ genotypes, which eventually lead to a penetrance reduction of the PEm genes expression, 2)polyembryony frequencies of the two populations were always statistically the same, no matter the environmentalconditions where they were grown, and 3) the trait´s inheritance model was validated

Propuesta para la documentación y sistematización del proceso administrativo de catálogos para una empresa distribuidora de medicamentos bajo la norma ISO 9001:2008.

TESINA A7.179

Prevalence of SARS-CoV-2 infection in Baja California, Mexico: Findings from a community-based survey in February 2021 in the Mexico-United States border.

Between March 2020 and February 2021, the state of Baja California, Mexico, which borders the United States, registered 46,118 confirmed cases of COVID-19 with a mortality rate of 238.2 deaths per 100,000 residents. Given limited access to testing, the population prevalence of SARS-CoV-2 infection is unknown. The objective of this study is to estimate the seroprevalence and real time polymerase chain reaction (RT-PCR) prevalence of SARS-CoV-2 infection in the three most populous cities of Baja California prior to scale-up of a national COVID-19 vaccination campaign. Probabilistic three-stage clustered sampling was used to conduct a population-based household survey of residents five years and older in the three cities. RT-PCR testing was performed on nasopharyngeal swabs and SARS-CoV-2 seropositivity was determined by IgG antibody testing using fingerstick blood samples. An interviewer-administered questionnaire assessed participants' knowledge, attitudes, and preventive practices regarding COVID-19. In total, 1,126 individuals (unweighted sample) were surveyed across the three cities. Overall prevalence of SARS-CoV-2 infection by RT-PCR was 7.8% (95% CI 5.5-11.0) and IgG seroprevalence was 21.1% (95% CI 17.4-25.2). There was no association between border crossing in the past 6 months and SARS-CoV-2 prevalence (unadjusted OR 0.40, 95%CI 0.12-1.30). While face mask use and frequent hand washing were common among participants, quarantine or social isolation at home to prevent infection was not. Regarding vaccination willingness, 30.4% (95% CI 24.4-3 7.1) of participants said they were very unlikely to get vaccinated. Given the high prevalence of active SARS-CoV-2 infection in Baja California at the end of the first year of the pandemic, combined with its low seroprevalence and the considerable proportion of vaccine hesitancy, this important area along the Mexico-United States border faces major challenges in terms of health literacy and vaccine uptake, which need to be further explored, along with its implications for border restrictions in future epidemics