Biology, a branch of science studying living things in all aspects, has a large scope. Besides covering a large content, it also includes abstract concepts in some matters. Especially in the issues of abstract and microscopic biology, various alternative terms are determined at different levels of education. This study aims at determining pre-service teachers’ alternative conceptions regarding the tRNA concepts on protein synthesis. 12 first year university students participated in the research. Semistructured interviews were conducted so as to determine the pre-service teachers’ alternative conceptions for the tRNA concept. On analyzing the data obtained through the interviews, it was found that the pre-service teachers had differing alternative conceptions for the concept of tRNA. Those conceptions were tabulated in categories.