Abstract
In genetics education, symbols are used for alleles to visualize them and to explain probabilities of progeny and inheritance paradigms. In this study, we identified symbol systems used in genetics textbooks and the justifications provided for changes in the symbol systems. Moreover, we wanted to understand how students justify the use of different symbol systems when solving genetics problems. We analyzed eight textbooks from three different countries worldwide. We then presented a genetics problem to eight 9th-grade students and probed their justifications for the use of different symbol systems. Our findings showed that there is no one conventional symbol system in textbooks; instead, symbol systems are altered along and within textbooks according to the genetic context. More importantly, this alteration is not accompanied by any explicit explanation for the alteration. Student interviews revealed that some students were able to identify the genetic context of each symbol system, whereas others, who were unable to do so, provided justifications based on different non-genetics-related reasons. We discuss the implications of our analysis for how multiple symbol systems should be presented in textbooks, and how they should be introduced in the classroom.
Highlights
External representations are used by scientists to communicate with one another and with the non-scientist population
We aimed to learn more about the symbol systems used to represent alleles in genetics textbooks, and to understand how students justify their use
We found several symbol systems for alleles coexisting along and across genetics textbooks
Summary
External representations are used by scientists to communicate with one another and with the non-scientist population. Using external representations in a flexible manner allows scientists to manipulate those representations, creating a working model that can be updated when new experimental results are obtained or a new understanding is reached [2]. It seems that the power of representations is rooted in the ability to transform them, an ability that is reserved for those who can comprehend the semiotic system. Students at various ages experience difficulties in interpreting and using scientific representations [5,6] They often misinterpret them, for example, they interpret an arrow in a scientific representation as a movement instead of a process or vice versa [7]. They sometimes think that a diagram representing a structure represents a complex process [8], and they often apply the subscript of an element in a chemical formula to the following element rather than the preceding one [5]
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