Reaching Struggling Introductory Biology Students with a Targeted Peer Tutoring Program

Low persistence in STEM majors has long been an area of concern for institutions and educational researchers. The transition from introductory to advanced courses has been identified as a particularly “leaky” point along the STEM pipeline. Students who struggle early in an introductory STEM course rarely show significant improvement over the remainder of the semester. This poor early performance can damage self-efficacy and result in disengagement in the course, negative perceptions of the field, and reduced persistence in the course. This study examined the wide impact of an optional peer tutoring specifically targeted at these students who experience early difficulties in a large- enrollment, introductory biology course. Outcomes were measured using a combination of course performance, course management system data, and self-report surveys. Students who regularly attended peer tutoring were found to have increased engagement in the course, more expert-like perceptions of biology, better exam performance, and increased persistence relative to their peers who were not attending the peer tutoring sessions. Implications of these findings for universities looking to offer targeted academic assistance are discussed

Stage-specific dynamic reorganization of genome topology shapes transcriptional neighborhoods in developing human retinal organoids

Summary: We have generated a high-resolution Hi-C map of developing human retinal organoids to elucidate spatiotemporal dynamics of genomic architecture and its relationship with gene expression patterns. We demonstrate progressive stage-specific alterations in DNA topology and correlate these changes with transcription of cell-type-restricted gene markers during retinal differentiation. Temporal Hi-C reveals a shift toward A compartment for protein-coding genes and B compartment for non-coding RNAs, displaying high and low expression, respectively. Notably, retina-enriched genes are clustered near lost boundaries of topologically associated domains (TADs), and higher-order assemblages (i.e., TAD cliques) localize in active chromatin regions with binding sites for eye-field transcription factors. These genes gain chromatin contacts at their transcription start site as organoid differentiation proceeds. Our study provides a global view of chromatin architecture dynamics associated with diversification of cell types during retinal development and serves as a foundational resource for in-depth functional investigations of retinal developmental traits

Rapid adaptive evolution of the diapause program during range expansion of an invasive mosquito.

In temperate climates, the recurring seasonal exigencies of winter represent a fundamental physiological challenge for a wide range of organisms. In response, many temperate insects enter diapause, an alternative developmental program, including developmental arrest, that allows organisms to synchronize their life cycle with seasonal environmental variation. Geographic variation in diapause phenology contributing to local climatic adaptation is well documented. However, few studies have examined how the rapid evolution of a suite of traits expressed across the diapause program may contribute to climatic adaptation on a contemporary timescale. Here, we investigate the evolution of the diapause program over the past 35 years by leveraging a natural experiment presented by the recent invasion of the Asian tiger mosquito, Aedes albopictus, across the eastern United States. We sampled populations from two distinct climatic regions separated by 6° of latitude (∼700 km). Using common-garden experiments, we identified regional genetic divergence in diapause-associated cold tolerance, diapause duration, and postdiapause starvation tolerance. We also found regional divergence in nondiapause thermal performance. In contrast, we observed minimal regional divergence in nondiapause larval growth traits and at neutral molecular marker loci. Our results demonstrate rapid evolution of the diapause program and imply strong selection caused by differences in winter conditions