Models of classroom assessment for course-based research experiences

Course-based research pedagogy involves positioning students as contributors to authentic research projects as part of an engaging educational experience that promotes their learning and persistence in science. To develop a model for assessing and grading students engaged in this type of learning experience, the assessment aims and practices of a community of experienced course-based research instructors were collected and analyzed. This approach defines four aims of course-based research assessment—(1) Assessing Laboratory Work and Scientific Thinking; (2) Evaluating Mastery of Concepts, Quantitative Thinking and Skills; (3) Appraising Forms of Scientific Communication; and (4) Metacognition of Learning—along with a set of practices for each aim. These aims and practices of assessment were then integrated with previously developed models of course-based research instruction to reveal an assessment program in which instructors provide extensive feedback to support productive student engagement in research while grading those aspects of research that are necessary for the student to succeed. Assessment conducted in this way delicately balances the need to facilitate students’ ongoing research with the requirement of a final grade without undercutting the important aims of a CRE education

Evidence for Segment-Nonspecific Packaging of the Influenza A Virus Genome

The influenza A virus genome is composed of eight negative-sense RNA segments (called vRNAs), all of which must be packaged to produce an infectious virion. It is not clear whether individual vRNAs are packaged specifically or at random, however, and the total vRNA capacity of the virion is unknown. We have created modified forms of the viral nucleoprotein (NP), neuraminidase (NA), and nonstructural (NS) vRNAs that encode green or yellow fluorescent proteins and studied the efficiency with which these are packaged by using a plasmid-based influenza A virus assembly system. Packaging was assessed precisely and quantitatively by scoring transduction of the fluorescent markers in a single-round infectivity assay with a flow cytometer. We found that, under conditions in which virions are limiting, pairs of alternatively tagged vRNAs compete for packaging but do so in a nonspecific manner. Reporters representing different vRNAs were not packaged additively, as would be expected under specific packaging, but instead appeared to compete for a common niche in the virion. Moreover, 3 to 5% of transduction-competent viruses were found to incorporate two alternative reporters, regardless of whether those reporters represented the same or different vRNAs — a finding compatible with random, but not with specific, packaging. Probabilistic estimates suggest that in order to achieve this level of dual transduction by chance alone, each influenza A virus virion must package an average of 9 to 11 vRNAs