Adaptive laboratory evolution typically involves the propagation of organisms asexually to select for mutants with the desired phenotypes. However, asexual evolution is prone to competition among beneficial mutations (clonal interference) and the accumulation of hitchhiking and neutral mutations. The benefits of horizontal gene transfer toward overcoming these known disadvantages of asexual evolution were characterized in a strain of Escherichia coli engineered for superior sexual recombination (genderless). Specifically, we experimentally validated the capacity of the genderless strain to reduce the mutational load and recombine beneficial mutations. We also confirmed that inclusion of multiple origins of transfer influences both the frequency of genetic exchange throughout the chromosome and the linkage of donor DNA. We built a simple kinetic model to estimate recombination frequency as a function of transfer size and relative genotype enrichment in batch transfers; the model output correlated well with the experimental data. Our results provide strong support for the advantages of utilizing the genderless strain over its asexual counterpart during adaptive laboratory evolution for generating beneficial mutants with reduced mutational load. IMPORTANCEOver 80 years ago Fisher and Muller began a debate on the origins of sexual recombination. Although many aspects of sexual recombination have been examined at length, experimental evidence behind the behaviors of recombination in many systems and the means to harness it remain elusive. In this study, we sought to experimentally validate some advantages of recombination in typically asexual Escherichia coli and determine if a sexual strain of E. coli can become an effective tool for strain development.

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<p>This research paper examines the role that teaching mediation plays in the destabilization and reconstruction of representations of the concept of light among primary education students. It investigates their comprehension of light as an entity that is transferred autonomously of the light source and the receiver. This problem has been studied with two groups of 8-9 year-old children. The experimental group (E.G) participated in a teaching process that aimed to lead pupils to the construction of a model compatible to the scientific own; the control group (C.G) followed traditional teaching methods. In all experimental situations studied the difference between pre-test and post-tests was significant for the subjects of the experimental group both at the level of explaining the light as independent entity and at the level of the stability of cognitive acquisitions. </p>

School choice research is abundant, but rarely incorporates students' experiences or perspectives. This study investigates a diverse group of students' school choice experiences as they applied to, gained admission to and enrolled in high school in Chicago Public Schools, which offers over 130 options. Adapting Ball and colleagues' (2012) concept of policy actor positionality, we analyzed the role of students' developmental and social statuses in students' school choice experiences. Students' policy encounters were developmentally consistent, but their admissions results and subsequent academic trajectories diverged by their socioeconomic status. We discuss these findings' developmental and equity implications for school choice policy. In recent decades, many urban districts have adopted intradistrict school choice policy, 1 which allows students and their parents to select a preferred public school rather than be assigned to one based on neighborhood attendance boundaries. Proponents argue that school choice can expand students' access to high quality schools, regardless of where they live (Betts & Loveless, 2005; Burke et al., 2013). Choice advocates laud its potential to boost student performance, since poorly performing schools ostensibly face the threat of declining enrollment and, eventually, closure (Manno, Finn & Vanourek, 1999). Researchers have investigated whether these claims have been realized, exploring topics such as the distribution of diverse students across schools of choice (e.g., Gold et al., 2010), on-time graduation rates (Lauen, 2009), and district-wide performance changes after school choice policy adoption (e.g., Cordes, 2017; Imberman, 2011).

The light is a separate entity in the area, independent sources that produce it and the effects it causes during its spread. In several research focused on representations of light that are children from 5 to 15 years found that these representations are often incompatible with the scientific model. 112 (60 boys and 62 girls) participated in this research where we studied representations of children 11-12 years on the light. As a technique of research we chose the directive individual interview. The results of the research show that children of 11-12 years, use different categories of representations for the light.