Undergraduate Textbook Representations of Meiosis Neglect Essential Elements

Abstract

The process of meiosis is an essential topic that secondary and postsecondary students struggle with. The important meiosis-related concepts of homology, ploidy, and segregation can be described using the DNA Triangle framework, which connects them to the multidimensional nature of DNA (chromosomal, molecular, and informational levels). We have previously established that undergraduate biology students typically fail to describe and/or link appropriate levels to their explanations of meiosis. We hypothesize that students' understanding mirrors the resources they are given – in other words, textbook figures often lack many of the important connections that experts include when talking about meiosis. Prior work showed that text in meiosis chapters typically fails to include many concepts that experts consider important, so we examined how textbook figures present meiosis concepts. We found that almost all textbook representations include the chromosomal level of DNA, but few include the other levels, even to illustrate concepts that are rooted in informational and/or molecular levels. In particular, the molecular level of DNA was absent from nearly all introductory textbook figures examined, and the informational level was seldom depicted in mid/upper-level textbook figures. The previously established deficits in text portions of textbooks are clearly not compensated by their accompanying illustrations.

Teaching meiosis with the DNA triangle framework: A classroom activity that changes how students think about chromosomes

“…[12][13][14] Learners, on the other hand, do not have the experience or the visual literacy skills of experts [15][16][17][18] and may not learn as much from static textbook images as instructors would hope. Bolstered by previous research findings about the deficiencies of traditional textbooks in illustrating the molecular level of meiotic processes, 11,19 we posit that students struggle to understand meiosis because they see (when looking at textbook images as well as when picturing the process in their minds) chromosomes in a twodimensional way-usually as red or blue blob-like structures. Chromosomes, however, are incredibly complex molecules of DNA and protein.…”

“…Traditional classroom activities and textbook illustrations of meiosis focus almost exclusively on the chromosomal and informational level and fail to incorporate the molecular level. 19,39 Students are exposed to these same sets of teaching materials time and time again and are rarely challenged to think about the underlying molecular processes that drive chromosomal behavior. We designed our novel set of materials using the DNA Triangle framework as a guide to help students "see" the underlying molecular structure (nucleotide sequence) of homologous chromosomes and explore how sequence similarity drives the process of crossing over.…”

“…Many textbook illustrations simply show a pair of homologous chromosomes, one red and one blue, lined up side-by-side (no physical interaction) and do not show individual strands of DNA nor how they invade and combine with a complementary strand on a non-sister chromatid. 19 Hand-held models such as pop-bead chromosomes show crossing over by exchanging red and blue beads on non-sister chromatids; this model serves to strengthen a common misconception or misunderstanding about crossing over, namely that chromatid pieces simply break off and exchange places.…”

“…Unfortunately, collegelevel biology textbooks typically describe (by the text as well as the visual representations) important concepts like ploidy, homology, and segregation at only the chromosomal level. 11,19 Typical models or activities designed to help students learn meiosis often involve manipulatives such as pool noodles, pop-beads, or socks. 7,20,21 While a hands-on "active-engagement" approach is certainly better than a straight lecture, [22][23][24] most models fall short because they mainly focus on the chromosomal level and only hint at the informational level.…”

“…Yet the underlying molecular nature of the crossing-over process is rarely described or illustrated in undergraduate biology textbooks, especially introductory levels. 11,19 Molecular-level interactions that drive cellular processes cannot be directly visualized and, thus, may be "black boxes" for the novice student trying to comprehend these processes. We hypothesized that revealing the molecular level would help students understand how and why homologous DNA sequence drives the process of crossing over and why it is essential for proper segregation.…”