Reforms within science education strive to shift early science instruction (K-2) so students have ample sense-making opportunities to construct scientific explanations. Classroom discussions play a key role in supporting these endeavors. This requires that classroom discussions are shaped in ways that foster scientific instruction and learning. In this study, we take a social semiotic perspective on Goffman's notions of frames and participation framework to explore how a first-grade teacher accessed and supported his students' scientific explanation construction within whole-class discussions. Our research questions ask how scientific explanations are framed during science discussions and how this framing influences student scientific explanations and participation in science talk. Evidence suggests that the teacher's framing resulted in miscues regarding the frame and participation framework necessary to participate in the discussion. When students encountered these miscues, their participation was thwarted and opportunities for articulating scientific sense-making were lost. Implications for this study identify the importance of semiotic resources for framing science instruction during classroom discussions and the architecture of interactional spaces.