The molecular genetic toolkit of the Mexican axolotl, a classic model organism, has matured to the point where it is now possible to identify genes for mutant phenotypes. We used a positional cloning–candidate gene approach to identify molecular bases for two historic axolotl pigment phenotypes: white and albino. White (d/d) mutants have defects in pigment cell morphogenesis and differentiation, whereas albino (a/a) mutants lack melanin. We identified in white mutants a transcriptional defect in endothelin 3 (edn3), encoding a peptide factor that promotes pigment cell migration and differentiation in other vertebrates. Transgenic restoration of Edn3 expression rescued the homozygous white mutant phenotype. We mapped the albino locus to tyrosinase (tyr) and identified polymorphisms shared between the albino allele (tyr a) and tyr alleles in a Minnesota population of tiger salamanders from which the albino trait was introgressed. tyr a has a 142 bp deletion and similar engineered alleles recapitulated the albino phenotype. Finally, we show that historical introgression of tyr a significantly altered genomic composition of the laboratory axolotl, yielding a distinct, hybrid strain of ambystomatid salamander. Our results demonstrate the feasibility of identifying genes for traits in the laboratory Mexican axolotl.

Graduate teaching assistants (GTAs) are used extensively as instructors in higher education, yet their status and authority as teachers may be unclear to undergraduates, to administrators, and even to the GTAs themselves. This study explored undergraduate perception of classroom instruction by GTAs and professors to identify factors unique to each type of instructor versus the type of classes they teach. Data collection was via an online survey composed of subscales from two validated instruments, as well as one open-ended question asking students to compare the same class taught by a professor versus a GTA. Quantitative and qualitative results indicated that some student instructional perceptions are specific to instructor type, and not class type. For example, regardless of type of class, professors are perceived as being confident, in control, organized, experienced, knowledgeable, distant, formal, strict, hard, boring, and respected. Conversely, GTAs are perceived as uncertain, hesitant, nervous, relaxed, laid-back, engaging, interactive, relatable, understanding, and able to personalize teaching. Overall, undergraduates seem to perceive professors as having more knowledge and authority over the curriculum, but enjoy the instructional style of GTAs. The results of this study will be used to make recommendations for GTA professional development programs.

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This study explored student ratings of instruction by GTAs and faculty members to see whether perceptions differed by instructor type, whether they changed over a semester, and whether certain instructor traits were associated with student perception of their instructor's teaching effectiveness or how much they learned from their instructor.

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Who is the ideal teacher? Am I? Similarity and difference in perception of education regarding the qualities of a good teacher and of their own qualities as techers. Teachers and Teaching, 13, 441-464. Austin, A. E. (2002). Preparing the next generation of faculty: graduate school as socialization to the academic career.

Graduate teaching assistants (GTAs) are often used as instructors in undergraduate introductory science courses, particularly in laboratory and discussion sections associated with large lectures. These GTAs are often novice teachers with little opportunity to develop their teaching skills through formal professional development. Focused self-reflection about end-of-semester teaching evaluations may be an important informal supplement to teacher training. To inform this practice, we explored the instructional behaviors that undergraduates perceived as most important for GTAs’ teaching effectiveness in laboratory courses. In spring semester 2012, 1159 undergraduates in freshman-level biology lab courses rated their GTAs on 21 instructional behaviors, the GTAs’ teaching effectiveness, the amount the student learned, and their expected grade in the laboratory. Using linear mixed models, we found that instructional behaviors related to the categories of teaching techniques and interpersonal rapport best predicted student ratings of GTAs’ teaching effectiveness. GTAs or other novice teachers can use this information to identify specific areas for instructional improvement when considering student feedback about their teaching.