Making sense of Mendelian genes

An enduring legacy from the heyday of Mendelian genetics is talk of ‘genes for'. Such talk suggests straightforwardly that genes make characters. But for over a century, thoughtful biologists have insisted such an understanding is mistaken. For them, a gene is a chromosomal difference that, when internal and external environments are otherwise equal, makes a phenotypic difference; ‘genes for’ talk is but shorthand for this more complex understanding. This paper examines the remarkable durability of the disowned, deterministic character-making understanding, placing particular emphasis on the role of the traditional, start-with-Mendel curriculum in investing that understanding with a heuristic power which later teaching may never fully displace. The paper also reports on recent experimental work exploring the potential of a reordered curriculum for teaching genetics without bolstering genetic determinism.