Identification and remediation of student difficulties with quantitative genetics.

Abstract

Genetics has been identified as a subject area which many students find difficult to comprehend. The researcher, who is also a lecturer at the University of KwaZulu-Natal, had noted over a number of years that students find the field of quantitative genetics particularly challenging. The aim of this investigation was two-fold. Firstly, during the diagnostic phase of the investigation, to obtain empirical evidence on the nature of difficulties and alternative conceptions that may be experienced by some students in the context of quantitative genetics. Secondly, to develop, implement and assess an intervention during the remediation phase of the study which could address the identified difficulties and alternative conceptions. The research was conducted from a human constructivist perspective using an action research approach. A mixed-method, pragmatic paradigm was employed. The study was conducted at the University of KwaZulu-Natal over four years and involved third-year students studying introductory modules in quantitative genetics. Empirical evidence of students' conceptual frameworks, student difficulties and alternative conceptions was obtained during the diagnostic phase using five research instruments. These included: free-response probes, multiple-choice diagnostic tests, student-generated concept maps, a word association study and student interviews. Data were collected, at the start and completion of the modules, to ascertain the status of students' prior knowledge (prior knowledge concepts), and what they had learnt during the teaching of the module (quantitative genetics concepts). Student-generated concept maps and student interviews were used to determine whether students were able to integrate their knowledge and link key concepts of quantitative genetics. This initial analysis indicated that many students had difficulty integrating their knowledge of variance and heritability, and could not apply their knowledge of quantitative genetics to the solution of practical problems. Multiple-choice diagnostic tests and interviews with selected students were used to gather data on student difficulties and alternative conceptions. The results suggested that students held five primary difficulties or alternative conceptions with respect to prior knowledge concepts: (1) confusion between the terms variation and variance; (2) inappropriate association of heterozygosity with variation in a population; (3) inappropriate association of variation with change; (4) inappropriate association of equilibrium with inbred populations and with values of zero and one; and, (5) difficulty relating descriptive statistics to graphs of a normal distribution. Furthermore, three major difficulties were detected with respect to students understanding of quantitative genetics concepts: (1) students frequently confused individual and population measures such as breeding value and heritability; (2) students confused the terms heritability and inheritance; and, (3) students were not able to link descriptive statistics such as variance and heritability to histograms. Students found the concepts of variance and heritability to be particularly challenging. A synthesis of the results obtained from the diagnostic phase indicated that many of the difficulties and alternative conceptions noted were due to confusion between certain terms and topics and that students had difficulty with the construction and interpretation of histograms. These results were used to develop a model of the possible source of students' difficulties. It was hypothesized and found that the sequence in which concepts are introduced to students at many South African universities could be responsible for difficulties and alternative conceptions identified during the study, particularly the inappropriate association of terms or topics. An intervention was developed to address the identified difficulties and alternative conceptions. This intervention consisted of a series of computer-based tutorials and concept mapping exercises. The intervention was then implemented throughout a third year introductory module in quantitative genetics. The effectiveness of the intervention was assessed using the multiple-choice diagnostic tests and interview protocols developed during the diagnostic phase. The knowledge of the student group who participated in the intervention (test group) was compared against a student group from the previous year that had only been exposed to conventional teaching strategies (control group). t-tests, an analysis of covariance and a regression analysis all indicated that the intervention had been effective. Furthermore, an inductive analysis of the student responses indicted that most students understanding of the concepts of variance, heritability and histograms was greatly improved. The concept maps generated by students during the remediation phase, and data from the student interviews, provided an indication of the nature and extent of the conceptual change which had occurred during the teaching of the module. The results showed that most of the conceptual change could be classified as conceptual development or conceptual capture and not conceptual exchange. Furthermore, it seemed that conceptual change had occurred when considered from an epistemological, ontological and affective perspective, with most students indicating that they felt they had benefited from all aspects of the intervention. The findings of this research strongly suggest an urgent need to redesign quantitative genetics course curricula. Cognisance should be taken of both the sequence and the manner in which key concepts are taught in order to enhance students' understanding of this highly cognitively demanding area of genetics.