Nowadays it is increasingly required insertion History of Science on content to be worked in education, which raises many doubts and difficulties on the teachers did not have that content in their initial training. This work results from a qualitative empirical study aimed to investigate how a teacher of Biology and Science in a public school in the city of Bauru - SP was not in their initial training courses relating to the History of Science, mobilizes their knowledge to enter such an approach in their teaching practice. In the research methodology used as its theme the history of DNA present in the materials and also conduct open interviews and field notes to identify the knowledge involved in teaching practice and was adopted as the theoretical framework of Maurice Tardif’s Docent Knowledge. The results showed that even with difficulties arising from gaps in initial training, the teacher resorted to their experiential knowledge to meet these needs in addition to appropriate knowledge from the programs and textbooks, but its shortcomings make it difficult to analyze more critically. Thus, these data lead us to a reflection on the role of textbooks for these teachers is the process by which the consolidation of the knowledge they constructed.