The purpose of this study was to (a) develop an analytical framework that represents classroom talk and questioning in science, (b) find out how teachers use questioning to engage their students in thinking about conceptual content that enables the construction of knowledge, and (c) identify the various forms of feedback provided by teachers in the follow-up move of the initiation-response-follow-up format of teaching exchange. Several lessons from Year 7 classes were observed across a variety of lesson structures such as expository teaching, whole-class discussions, laboratory demonstration, and hands-on practical work. The lessons were audiotaped and videotaped. Transcripts of the lessons were made and analysed, with particular attention paid to interactions that involved questions. Using the "Questioning-based Discourse" analytical framework developed in this study, four different types of feedback were identified. Interactional issues related to ways of speaking and questioning that encourage student responses and thinking are addressed. This information provides a description of what constitutes effective discourse in science teaching and learning, and will also be useful for both teachers and teacher-educators in identifying an appropriate repertoire of skills for subsequent teacher education and professional development. (Contains 7 tables and 1 figure.)