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. 2022 Mar;21(1):ar14.
doi: 10.1187/cbe.21-01-0009.

Secondary Students' Reasoning on Pedigree Problems

Justin Timm  1 , Katharina Wools  1 , Philipp Schmiemann  1
Affiliations

Secondary Students' Reasoning on Pedigree Problems

Justin Timm et al. CBE Life Sci Educ. 2022 Mar.

Abstract

Pedigree problems are typical genetics tasks in schools. They are well suited to help students learn scientific reasoning, representing realistic genetic problems. However, pedigree problems also pose complex requirements, especially for secondary students. They require a suitable solution strategy and technical knowledge. In this study, we examined the approaches used by N = 89 secondary school students when solving two different pedigree problems. In our qualitative analysis of student responses, we examined how two groups of secondary students with varying degrees of experience in genetics constructed arguments to support their decisions. To do so, we categorized I = 516 propositions from students' responses using theory- and data-driven codes. Comparison between groups revealed that "advanced genetics" students (n = 44) formulated more arguments, referred more frequently to specific family constellations, and considered superficial pedigree features less often. Conversely, "beginning genetics" students did not use a conclusive approach of step-by-step falsification but argued for the mode of inheritance they believed was correct. Advanced genetics students, in contrast to beginners, to some extent used a falsification strategy. Finally, we demonstrate which family members students used in their decisions and discuss a variety of typical but unreliable arguments.

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Figures

FIGURE 1.
FIGURE 1.
Pedigrees used in the paper-and-pencil tests.
FIGURE 2.
FIGURE 2.
Mosaic plot showing the structure of students’ arguments. The relationship between the inheritance mentioned in the argument and the data used to prove that claim is shown separately for each group. The diagram maps all possible combinations of pedigree features and claims regarding the inheritance, while the area of each box represents how often that specific combination was found among students’ statements. Thin lines without percentages indicate that a specific combination was not found. AD, autosomal dominant inheritance; AR, autosomal recessive inheritance; XD, X-linked dominant inheritance; XR, X-linked recessive inheritance; Y, Y-linked inheritance.
FIGURE 3.
FIGURE 3.
Representation of the frequency with which students mentioned individual family members in their arguments regarding the present mode of inheritance separately for each pedigree and group. The frequencies are shown in the pedigrees by the color and size of the points. Mentions of individual family members in the pedigree showing an autosomal recessive trait by (a) beginning genetics students and (b) advanced genetics students. Mentions of individual family members in the pedigree showing an autosomal dominant trait by (c) beginning genetics students and (d) advanced genetics students.
FIGURE 4.
FIGURE 4.
Number of conclusive arguments per person and pedigree. Individuals were counted as a function of group membership. Colors indicate which proportion of individuals marked the correct inheritance in an attached multiple-choice item.
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