The teaching of genetics has not been effective in promoting a scientifically acceptable understanding of basic genetics concepts. This study addresses that gap by reporting on topic-specific pedagogical content knowledge (PCK) enacted by a teacher educator as she teaches a content course on basic genetics concepts to fourth-year pre-service teachers. A qualitative case study was conducted to investigate the nature of manifested content specific component interactions and the possible value in enhancing the learning of basic genetics concepts. This study is rooted in the refined consensus model of PCK with a focus on the enacted PCK (ePCK). The PCK framework informed the understanding of the ePCK components in this study as well as the design of an ePCK rubric and other qualitative analysis enablers. They were used in this study to analyze the data captured through written Content Representations (CoRes), video-recorded lectures, and interviews over a 3-year period. The findings indicate that the ePCK manifested in planning and teaching was reasoned pedagogically and of high quality and more so, perceived to enhance students' learning. By year three, revealed ePCK consisted mostly of proficient and sophisticated ePCK with coherent component interactions that are indicative of enriched explanations and learning tasks such as the sequencing of the concepts, well-thought-out instructional representations, and learner prior knowledge. Therefore, the generated insights are strong evidence about the kind of teaching that can significantly address misconceptions and what makes genetics concepts difficult to learn--a knowledge that should be significant to others in the field.