Research in Science Education

, Volume 43, Issue 4, pp 1361–1375

Is DNA Alive? A Study of Conceptual Change Through Targeted Instruction

Authors

    • Department of Science, Technology, Engineering & Mathematics (STEM) EducationUniversity of Massachusetts Dartmouth
  • Sharyn K. Freyermuth
    • Department of BiochemistryUniversity of Missouri (MU)
  • Marcelle A. Siegel
    • Department of BiochemistryUniversity of Missouri (MU)
    • Department of Learning, Teaching, and Curriculum, MU Science Education CenterUniversity of Missouri (MU)
  • Kemal Izci
    • Department of Learning, Teaching, and Curriculum, MU Science Education CenterUniversity of Missouri (MU)
  • J. Chris Pires
    • Division of Biological SciencesUniversity of Missouri (MU)
Article

DOI: 10.1007/s11165-012-9311-4

Cite this article as:
Witzig, S.B., Freyermuth, S.K., Siegel, M.A. et al. Res Sci Educ (2013) 43: 1361. doi:10.1007/s11165-012-9311-4

Abstract

We are involved in a project to incorporate innovative assessments within a reform-based large-lecture biochemistry course for nonmajors. We not only assessed misconceptions but purposefully changed instruction throughout the semester to confront student ideas. Our research questions targeted student conceptions of deoxyribonucleic acid (DNA) along with understanding in what ways classroom discussions/activities influence student conceptions. Data sources included pre-/post-assessments, semi-structured interviews, and student work on exams/assessments. We found that students held misconceptions about the chemical nature of DNA, with 63 % of students claiming that DNA is alive prior to instruction. The chemical nature of DNA is an important fundamental concept in science fields. We confronted this misconception throughout the semester collecting data from several instructional interventions. Case studies of individual students revealed how various instructional strategies/assessments allowed students to construct and demonstrate the scientifically accepted understanding of the chemical nature of DNA. However, the post-assessment exposed that 40 % of students still held misconceptions about DNA, indicating the persistent nature of this misconception. Implications for teaching and learning are discussed.

Keywords

Deoxyribonucleic acidDNAConceptual changeAssessmentStudent conceptions

Introduction

Students tend to hold alternative conceptions in science that may not align with those of the scientific community. It is imperative that we are able to identify and confront these conceptions; however, educators lack the appropriate tools to do so in many science areas (Richardson 2005). There are few investigations that have identified students’ alternative conceptions in biotechnology, e.g., concerning stem cells, cloning, and genetics (Concannon et al. 2010; Halverson et al. 2010; Heselmans 2001; McHughen and Wager 2010; Shaw et al. 2008). While a conceptual instrument specifically designed to elicit student understanding in biotechnology was previously developed (Witzig et al. 2011), having an innovative assessment to uncover students’ alternative conceptions is only a first step in the learning process. Current practices in science education promote the implementation of multiple strategies to assess student learning (National Research Council 2001). Instructors need to adapt instruction in several different ways once alternative conceptions are identified and monitor students’ progress throughout.

One of the innovative ways to identify students’ preconceptions, use them to modify instruction, and monitor students’ progress, is the use of formative assessment. Research on formative assessment has demonstrated improvement in both the effectiveness of teachers’ instruction and in students’ learning (Black and Wiliam 1998). Black and Wiliam (2009) define formative assessment as:

Practice in a classroom is formative to the extent that evidence about student achievement is elicited, interpreted, and used by teachers, learners, or their peers, to make decisions about the next steps in instruction that are likely to be better, or better founded, than the decisions they would have taken in the absence of the evidence that was elicited (p. 9).

Building on Black and Wiliam’s (1998) research, Ruiz-Primo and Furtak (2007) proposed a formative assessment cycle composed of the following stages: (1) the elicitation of students’ ideas by using various strategies such as questioning, (2) the response of students, (3) the interpretation of students’ responses by the instructor, (4) the use of elicited and interpreted responses to design instruction, and (5) assessing students’ understanding of concepts to plan the next step of instruction. The effective use of the formative assessment cycle provides opportunities for instructors to monitor students’ learning and to plan instructional activities to improve students’ learning.

Adapting instruction based on students’ understanding is especially critical for core ideas in integrated science disciplines. Biotechnology is an interdisciplinary field drawing on science (biology and chemistry), technology, engineering, and mathematics (STEM) fields. Current reform documents encourage “crosscutting concepts” to help students develop a framework for learning across disciplines (National Research Council 2011). Identifying core ideas that students have difficulties with and developing ways to attend to these learning difficulties is central to this framework. Our research has revealed that students have difficulty understanding the chemical nature of deoxyribonucleic acid (DNA) (Rebello et al. 2012; Witzig et al. 2011). Understanding the fundamentals of DNA is critical for students to comprehend more complex applications of DNA, such as genetic engineering (National Research Council 2008). The focus of this study is to uncover students’ alternative conceptions about DNA and investigate the conceptual change that occurred longitudinally over the course of a semester through targeted innovative instruction.

The theoretical framework that guides this study is conceptual change (Hewson 1981; Gilbert and Watts 1983; Smith et al. 1993). Conceptual change is a process of meaningful science learning that asks learners to re-evaluate, re-arrange, and replace existing misconceptions in order to comprehend scientifically acceptable conceptions (Smith et al. 1993). According to Smith et al. (1993), misconceptions are: (a) originated from prior ideas, (b) stable and resistant to change, (c) impede future learning, and (d) need to be replaced with scientific conceptions. We know through research that students enter classrooms with prior conceptions about science. Hewson and Lemberger (1999) describe conceptions as unobservable “mental structures” that a person adopts or constructs (p. 509). Taken collectively, these conceptions and their interactions comprise a learner’s “conceptual ecology” (Hewson and Lemberger 1999, p. 509). Learners evaluate new information based on prior conceptions and re-evaluate prior information based on new information. Research has shown that some students have difficulty changing their existing conceptions when confronted with new ideas, especially if they do not understand or accept the new ideas (Lewis et al. 2000). The foundation of conceptual change theory posits that students need to be dissatisfied with prior conceptions; they should comprehend the new conceptions; new conceptions should be reasonable to them; and new conceptions should better make meaning to their experience and observations in order to replace the ideas with more plausible new ideas (Posner et al. 1982). However, more recent work builds on this idea and suggests that cognitive, motivational, and contextual factors also play a role in student’s conceptual change (Scott et al. 2007). Instructors, once aware that their students hold alternative conceptions in science, need to confront these conceptions with targeted instructional interventions to foster student learning. The students need to be aware of their alternative conceptions but also be motivated to adopt the new, scientifically correct conception. The formative assessment cycle is an effective strategy that encourages learners to construct new ideas, reflect on them, and re-evaluate their prior ideas to improve learning. Providing real-world contextual applications to foster conceptual change is critical.

The purpose of this study was to examine the nature of student conceptions of the properties of DNA. The teaching interventions and assessments were specifically designed to confront student misconceptions and allow the students opportunities to reflect on their ideas in light of the scientific evidence.

Methodological Design

Research Questions

The overarching research question for this study is: what is the nature of student conceptions of the properties of DNA? To address this question, we focused on the following sub-questions: (1) what is the nature of student conceptions of DNA pre- and post-instruction? and, (2) in what ways do classroom discussions and activities influence student conceptions of DNA?

The Nature of the Course

The context for the study was a large enrollment biochemistry course for nonbiochemistry majors, Biotechnology in Society. Two key instructional goals of this course are employed to: (a) help students construct accurate scientific ideas and (b) to enhance their reasoning skills to make evidence-based decisions about controversial issues in biotechnology. This course does not utilize a textbook but instead uses online readings and interactive websites. The course is structured to include interactive lectures, case discussions, hands-on activities, and independent projects. All topics are considered from a scientific point of view while discussing their impact on society.

Our participants included students enrolled in one of two semesters of Biotechnology in Society (n = 110 and 118). The first- through fourth-year students enrolled in this course pursued a wide variety of majors, from Agricultural Economics to Hotel and Restaurant Management to Journalism to Plant and Animal Sciences. The student demographic was representative of the enrollment in College of Agriculture which is approximately 46 % female, 6 % black, 0.9 % Hispanic, 2 % Asian, and 86 % Caucasian. Approximately 37 % of the students were first-generation college students. All participants in this study provided informed consent, and all names have been removed from the data and given pseudonyms to protect their anonymity.

The Nature of the Assessments

The three main assessments used to help students understand the chemical nature of DNA were the extraction of DNA from bananas, the Griffith experiment, and having students respond to other students’ statements concerning "is DNA alive?" These assessments were placed strategically within instruction of the course and came after a conceptual pretest and before a posttest.

The DNA extraction from bananas was done after 2 days of instruction about the chemical nature of DNA, its structure, and its function. This allowed the students to take an abstract concept, the structure and function of a molecule that they could not see, and actually extract the molecule themselves. Although this experiment does not allow them to see the molecular structure of DNA, they were asked to indicate what the purpose of each step in the extraction process was, linking reagents and procedures to the chemical structure of the DNA. And this does allow them to see that this physical substance, DNA, does reside inside cells and can be extracted.

The Griffith experiment is a conceptually very difficult exercise for the students. The activity takes place 2 weeks after the DNA extraction, and materials taught in class in the intervening lessons included DNA replication, cellular replication, and translation of DNA into proteins. The goal for this assessment is to underscore the idea that the DNA in a cell contains instructions for proteins and if that DNA is transferred to another cell, it retains the instructions to make the same proteins. We had previously taught the components of this information in a lecture, but this allows the students to walk through a specific experiment that shows this concept and to synthesize the material they learned to come to the correct conclusion.

The final assessment, asking students to respond to other students’ answers to "is DNA alive?" allows students to confront a variety of alternative conceptions, after they have worked through the DNA extraction, Griffith experiment and lessons on DNA structure and function. Given answers that are both correct and incorrect, the students are confronted with diverse answers and must use their synthesized knowledge to respond.

Data Collection and Analysis Methods

This research was guided using case study methodology (Yin 2003). We analyzed data from all participants in the study for emergent trends and themes. Student trends on pre-/post-assessments were summarized in charts. We then used individual case profiles to represent the themes. Additionally, we use negative case analysis to ensure that we have accurately represented the students in the study in our case profiles.

Four sources of data informed this research: (1) a pre-/postconceptual understanding instrument, (2) semi-structured student interviews, (3) course exams, and (4) in-class embedded assessments. (1) A previously developed conceptual understanding instrument was given two times during the semester as a pre-/post-assessment (Witzig et al. 2011). The instrument is known as the biotechnology instrument for knowledge elicitation (BIKE). The BIKE had previously been tested for validity and reliability using standard measures including internal consistency of items, inter-rater reliability, item analysis, and alignment with research-based designed principles. Two questions specifically related to the chemical nature of DNA were analyzed (Q7 and Q33). Frequency of student responses on the pre- and posttests (n = 107) within each category (problematic, adequate, and justified) were calculated and represented as a percent of all participants’ responses. For statistical analysis, we ran paired sample t tests for each category on each question for a total of six and applied a Bonferroni correction. (2) Mid-semester, we conducted semi-structured student interviews following guidelines in Patton (2002). (3) Student responses on course exam questions related to the chemical nature of DNA were collected and analyzed. (4) Student responses to in-class embedded assessments designed to specifically confront student misconceptions about DNA were collected and analyzed. The questions on these assessments were distinct from those on the pre-/posttests. These assessments were developed using research-based design principles (Rebello et al. 2012). The following steps outline the data analysis phase: (1) data analysis began during the data collection period. Student responses on assessments informed interview questions as well as instructional approaches; (2) after transcribing and analyzing the data, we produced case profiles for students’ conceptions of DNA; (3) we then looked across case profiles for patterns or disconfirming cases; (4) Finally, we established a set of themes in response to the research questions. While we acknowledge the potential for bias and alternative interpretations in any research study, we have taken steps to minimize these concerns and have established that our study meets criteria for trustworthiness (Lincoln and Guba 1985). For example, our data collection and analysis methods included both triangulation of data sources as well as researcher consensus on coding schemes. Additionally, we have employed negative case analysis to ensure that we have accurately represented the students in the study in our case profiles.

Findings

Through our investigation, we have established that students have difficulty with understanding the chemical nature of DNA. We provide evidence that this concept can be a persistent misconception among students, can impede future learning, and needs to be replaced with scientifically acceptable conception. The results below are organized around each of our research questions.

RQ1: What Is the Nature of Student Conceptions of DNA Pre- and Post-instruction?

We used a conceptual understanding instrument, the BIKE, (Witzig et al. 2011) to elicit student’s ideas about DNA pre-instruction. Specifically, there were two questions out of 35 that targeted the chemical nature of DNA. First, a basic question was posed to elicit student understanding: “Q7: DNA is a chemical and is not alive. True or false, explain your answer.” The scientifically correct response to this question is: true, DNA is a chemical; it is not alive, though it is essential for living things to carry out their cellular functions. Students should understand that a cell is the smallest unit of life, and that a cell contains chemical components, including DNA. Then, a more context-based question was posed that situated the concept in a real-world example: “Q33: DNA can be extracted from a dead animal frozen in Arctic ice. True or false, explain your answer.” Here, the scientifically correct answer is: true, DNA does not die along with the animal, and the information contained within the chemical structure of DNA can be used for several purposes, including species identification, etc. Students can draw on their understanding of forensics to apply this situation.

The results of the pretest revealed that over 60 % of students held a problematic conception of the chemical nature of DNA at the beginning of the course while only 8 % provided a well-justified, correct response (Fig. 1).
https://static-content.springer.com/image/art%3A10.1007%2Fs11165-012-9311-4/MediaObjects/11165_2012_9311_Fig1_HTML.gif
Fig. 1

Student conceptions of whether DNA is alive pre- and post-instruction. Problematic response was scientifically incorrect or partially incorrect, adequate response was accepted as scientifically correct but could be incomplete, justified response was accepted as scientifically correct and well justified, percent the frequency of student responses in that category compared with the whole class (n = 107). *p < 0.001, the change in problematic and justified responses are both statistically significant. Adequate responses are not statistically significant at a p > 0.05

Our scoring scheme included a three-point scale where “problematic” indicated a response was “scientifically incorrect, or partially incorrect,” an “adequate” response was “accepted as scientifically correct, but could be incomplete,” and a “justified” response was “accepted as scientifically correct, and well-justified.” The results shown in Fig. 1 represent the percent of student responses to the basic question of whether DNA is alive, Q7. A typical problematic student response is embodied in Alyssa’s pretest answer, “false, DNA is a living organism.” Whereas, a typical justified response on the posttest can be shown with Marcus’s response, “true, the chemical DNA is found in all living things, but the DNA chemical itself is not living.” What is encouraging is that problematic student responses decreased significantly by the end of the course while justified responses increased significantly (Fig. 1). However, our results reveal that even at the end of the course, 40 % of students still hold a problematic conception and believe that DNA is alive.

There was a range of responses given to the question of DNA being alive with about 20 % of those in the “adequate” category. For example, Devin on the pre-BIKE responds, “true, DNA is the genetic makeup of what you are talking about.” Here, nothing in Devin’s response is incorrect, and he identifies DNA as the genetic material. However, his answer is just adequate because he does not justify his response. On the post-BIKE, Devin elaborates on his response to this question and provides a “justified” response, “true, DNA is not alive and only contains the genetic make-up of organisms. It is bound together by hydrogen bonds that can easily be broken apart.” Here, Devin explicitly states that DNA is not alive, again identifies it as the genetic material, but then elaborates on his response by providing evidence for the chemical nature of DNA by describing the hydrogen bonding that holds the two strands of DNA together. Therefore, Devin’s profile shows a trend from adequate to justified throughout the course of instruction.

On the BIKE, we added the context-based question (Q33) about the possibility of extracting DNA from a dead animal frozen in Arctic ice to see if students could apply their knowledge of the chemical nature of DNA in a real-world application. The overall student results are found in Fig. 2.
https://static-content.springer.com/image/art%3A10.1007%2Fs11165-012-9311-4/MediaObjects/11165_2012_9311_Fig2_HTML.gif
Fig. 2

Student conceptions of whether DNA can be extracted from dead animal frozen in Arctic ice pre- and post-instruction. Problematic response was scientifically incorrect or partially incorrect, adequate response was accepted as scientifically correct but could be incomplete, justified response was accepted as scientifically correct and well justified, percent the frequency of student responses in that category compared with the whole class (n = 107). Problematic, adequate, and justified responses are not statistically significant at a p > 0.05

For this question, only about 20 % of pre-BIKE student responses were “problematic.” This is much lower than our findings from the question of DNA being alive (Fig. 1). The majority of responses fell in the adequate category with 42 % on the pre-BIKE and 54 % on the post-BIKE. There was a small, though not statistically significant, decline in justified responses from the pre- to the post-BIKE which can be explained with students providing adequate post-test responses with fewer examples to support their claims.

Devin’s response to pre-BIKE question 33, similar to his response above to Q7, was adequate, “True, the animal would be preserved since it is frozen so you would be able to extract the DNA from the animal.” Here, nothing about Devin’s response is incorrect, though he does not elaborate on his response with justification or examples. Mid-semester, we interviewed Devin and asked him to explain his response to this question:

Interviewer: Do you think that DNA can be extracted from a frozen dead animal from the Arctic?

Devin: Yes, because it’s not going to alter it or it’s going to be the same. The only thing I would question is, I guess the temperature isn’t going to have any effect on it. So I would have to say yes.

Interviewer: So it is possible to get the DNA?

Devin: Yes.

Interviewer: Can you explain why you think that you can still get the DNA?

Devin: It’s going to be preserved, I guess. I don’t remember exactly what it would be, but it’s going to be frozen, it’s going to be kept so that would be a possibility and it kind of goes back to the crime scene. People dig up in a grave or find somebody many years later that they are going to try and run DNA tests on so that’s the reason I think that it can be done.

Interviewer: Oh okay. So you’ve heard about this in forensics? Digging up graves?

Devin: Yes.

Here, Devin draws on his understanding of DNA from applying an example from crime scene investigations. He is familiar with the ability to run DNA tests on a person that has died, and transfers this knowledge to the example of the animal frozen in Arctic ice. However, he does not explicitly make the connection that the reason this is possible is because the DNA does not die along with the organism because it is simply a chemical. The genetic information is retained within the intact cells of the dead organism. Devin’s post-BIKE response to Q33 remains adequate, though from his justified response to question 7, it is clear that Devin now understands that DNA is chemical and is not alive.

The student responses on the pre- and posttests were analyzed quantitatively, and the results are depicted in Figs. 1 and 2. For Q7, represented in Fig. 1, we found a statistically significant decline in problematic student responses and a statistically significant increase in justified responses between the pre- and posttests. For Q33, represented in Fig. 2, we found no statistically significant difference in student responses on the pre- and posttests. Overall, our findings indicate that we have uncovered a persistent misconception. Students have difficulty understanding that DNA is a chemical and is not alive. Forty percent of students still held problematic responses to Q7, which explicitly asked students to explain whether DNA was alive (Fig. 1). While near 20 % of students held a problematic response to post-BIKE Q33, over 50 % of students responses were just adequate (Fig. 2). Providing a real-world context for students to apply their understanding of DNA resulted in less problematic responses, though students had difficulty articulating that the reason DNA could be extracted from a dead animal was because the DNA itself is a chemical and not alive (see Devin’s adequate response above). The instructional interventions that were designed to target student misconceptions, and resulted in the trends depicted in Figs. 1 and 2, are described below.

RQ2: In What Ways do Classroom Discussions and Activities Influence Student Conceptions of DNA?

Knowing that students had difficulties with understanding the chemical nature of DNA, specific instructional interventions were developed to target students’ alternative conceptions and to replace them with scientifically acceptable conceptions. The use of the formative assessments and the formative assessment cycle were critical to the development of instructional decisions. These interventions occurred during the course of instruction. Figure 3 outlines the instructional timeline that occurred throughout this study.
https://static-content.springer.com/image/art%3A10.1007%2Fs11165-012-9311-4/MediaObjects/11165_2012_9311_Fig3_HTML.gif
Fig. 3

Instructional timeline for confronting students’ misconceptions about DNA

We began with the identification of student misconceptions during the pilot-test phase of the BIKE development. This pilot test was administered as a posttest in the Spring semester prior to Fall semester where the instructional interventions were incorporated. The BIKE was revised and administered the following semester as a pre-test. Embedded assessments previously used in the course were revised to specifically target student misconceptions as well as to confront students with their own ideas. The course exams, which include both a group and an individual portion, were also modified to include opportunities to elicit student understanding. Both the group and individual portions of the exam assessed students’ understanding of the chemical nature of DNA. As a summative assessment, the post-BIKE was used to assess students’ understanding after instruction. Below, we provide case study examples from students in two groups: (1) students whose responses on the pre- and post-BIKE for both DNA questions remained problematic (i.e., left the course with a misconception about DNA) and (2) students whose responses on the pre- and post-BIKE questions showed a trend going from problematic to justified on both questions (i.e., experienced conceptual change during the course). Table 1 represents student responses at three key time points during the semester—the pretest, the post-banana DNA extraction embedded assessment probe, and the posttest (quantified pre-/posttest BIKE responses are represented in Figs. 1 and 2).
Table 1

Representative student responses to the “DNA is alive” questions on the pre-BIKE, the banana DNA extraction embedded assessment, and the post-BIKE (problematic (P), adequate (A), and justified (J))

Student

Pre-BIKE Q7: DNA is a chemical and is not alive. T or F, explain your answer

Pre-BIKE Q33: DNA can be extracted from a dead animal frozen in Arctic ice. T or F, explain your answer

Banana DNA: thinking about the DNA that you just isolated from banana: is DNA alive? Why or why not?

Post-BIKE Q7: DNA is a chemical and is not alive. T or F, explain your answer

Post-BIKE Q33: DNA can be extracted from a dead animal frozen in Arctic ice. T or F, explain your answer

Trend

Alyssa

False, DNA is a living organism (P)

False, unless they are still warm on the inside (P)

No, it has to have a cell (P)

False, it is alive (P)

True, if it is frozen the body is restored (P)

Problematic to problematic

Lillian

False, this does not even make sense (P)

False, it will die by then (P)

DNA is alive, because it was constantly changing from one thing to another (P)

True, DNA is alive (P)

False, this statement does not make sense (P)

Problematic to problematic

Devin

True, DNA is the genetic makeup of what you are talking about (A)

True, the animal would be preserved since it is frozen so you would be able to extract the DNA from the animal (A)

The DNA from the banana is alive because the plant is alive and still bearing fruit. This is the genetic information that characterizes the banana (P)

True, DNA is not alive and only contains the genetic make-up of organisms. It is bound together by hydrogen bonds that can easily be broken apart (J)

True, the DNA will not be altered because the temperature has preserved the DNA. It is still able to be used and will not have any problems with it (A)

Adequate to justified

Marcus

False, DNA is the basic makeup for all living things, therefore DNA is alive (P)

False, when you die DNA is destroyed. Ice does not help preserve DNA like it does other things (P)

Yes, DNA is alive in the sense that it is replicating and trying to reproduce itself to continue living (P)

True, the chemical DNA is found in all living things but the DNA chemical itself is not alive (J)

True, although DNA stops replicating when an organism dies this does not cause the remaining DNA to disappear thus DNA from the preserved animal can be removed (J)

Problematic to justified

Justin

False, DNA is an acid not chemical (P)

True, DNA is still present in some tissues (P)

No, DNA is a chain of bases and nucleotides which make up a living organism, but it is not alive by itself (J)

True, DNA requires living material to be expressed (J)

True, there is still tissue with DNA present since DNA is not living (J)

Problematic to justified

Brayden

False, DNA is a living protein (P)

True, they can retrieve DNA from any tissue from a living organism (P)

Yes, DNA is living because it divides and informs (P)

True, DNA is not living but it takes a living organism to express the genes (J)

True, DNA is not living and can be good from any cell whether it was living or not or frozen (J)

Problematic to justified

Riley

False, DNA is not a chemical; it is part of a living organism and is therefore living (P)

False, the animal is not alive (P)

Yes, because it has cells that hold genes and can replicate (P)

True, DNA itself is not living but it exists in living organisms (J)

True, the animal still holds its DNA characteristics although it is no longer living (J)

Problematic to justified

The trend in student responses throughout the course is indicated in the far right column

In the course of instruction, embedded assessments can be used not only to find out what students know, but also to have them confront their misconceptions (Rebello et al. 2012). During the Biotechnology in Society course on day 6, students engaged in an experiment where they extracted DNA from bananas. This was at the end of the second week of instruction. On days 4 and 5 of the class, students had received instruction on the chemical make-up of DNA, DNA structure, and its function. Their weekly assignment was to go through the online animation at: http://www.dnaftb.org/dnaftb/19/concept/index.html “The DNA molecule is shaped like a twisted ladder.” The banana DNA experiment at the end of the week was a chance to tie the model of the chemical structure of DNA, which is an abstract concept to most of the students, to a hands-on activity which allowed them to see a physical substance. The experiment was inquiry based, and the students were required to relate the experiment to real-world applications. During the investigation the instructor worked with the students to have them conceptualize each of the steps of the protocol, making sense of the purpose of each reagent and/or step (from cell lysis to DNA precipitation).

Following the activity, the instructor of the course posed the following question: “thinking about the DNA that you just isolated from banana, is DNA alive? Why or why not?” For some students, this investigation was enough for them to confront their misconception. For example, Justin (whose overall trend was problematic to justified), replied, “no, DNA is a chain of bases and nucleotides which make-up a living organism, but it is not alive by itself.” After instruction and the activity, Justin came to the realization that DNA is a chemical, and describes DNA as a chain of bases. However others, who also share an overall trend from problematic to justified, still held misconceptions about DNA after this activity. Brayden writes, “yes, DNA is living because it divides and informs.” Riley responds, “yes, because it has cells that hold genes and can replicate.” For Brayden and Riley, they seem to confuse DNA with the characteristics of cells. They both referred to cells and/or the ability to divide or replicate. For most students that held problematic responses on the pre-BIKE like Brayden and Riley, this investigation did not motivate them or was not contextually based enough to allow them to adopt a new, more scientifically based conception of DNA.

On day 12 of the course, the students were engaged in another embedded assessment where the chemical nature of DNA was important for full understanding of the activity. The assessment was developed around the findings from the famous ‘Griffith experiment’ that showed that the information for a trait can exist outside of a live cell and that the information can be transferred to a new cell to express this trait (Griffith 1928). The information is a chemical—DNA. Briefly, the Griffith experiment showed that when a virulent bacterial strain was injected into a mouse, the mouse died, and the virulent bacteria could be isolated from the dead mouse. When a non-virulent bacterial strain was injected into the mouse, the mouse survived, and there was an absence of the bacteria in the mouse. When a heat-killed virulent bacterial strain was injected, the mouse again survived, and there was also an absence of bacteria in the mouse. However, the interesting results occurred when a heat-killed virulent strain was mixed with a non-virulent living bacterial strain and injected into the mouse. In this treatment, the mouse died and living virulent bacteria were isolated from the mouse. This experiment demonstrated not only DNA recombination and the process of transformation, but also that genetic material retains its information outside of a live cell (the DNA from the heat-killed virulent strain recombined with the DNA from the living non-virulent strain resulting in the virulent strain that killed the mouse).

During this embedded assessment, students worked in groups to answer questions that took them through the experiment and the purpose of each step. This culminated in the last and most important question, “What was the point of this experiment and how was it made?” Lillian, whose trend remained problematic throughout the course, responded:

The point was to find a vaccine to protect against pneumonia-causing bacterium. He isolated two strands and identified if they were smooth or rough. He then isolated it and put it in different situations to see if it lived or died.

Here, Lillian simply describes the context of the experiment that Griffith conducted. She did not seem to understand the major point that was made with the experiment. However, Marcus, whose profile was problematic to justified, responded, “Mice were injected with different forms of a pathogen. Found that when one form of the pathogen is destroyed by heat the DNA was released which can then be absorbed by other forms of bacteria.” Here, although Marcus does not utilize the correct scientific terminology (absorbed), his understanding of the experiment is clear. The DNA from the heat killed virulent strain recombined with the DNA from the living non-virulent strain.

Brayden (trend = problematic to justified), answered this question by stating, “the point is that the information for a trait can exist outside of a live cell and we can transfer that information to a new cell to express the trait.” Here, Brayden elaborated in his response and clearly understood the take-home message from the experiment. The genetic information contained in DNA can exist outside of a live cell and can be recombined to introduce a trait into a new organism. This is the process of transformation, and an important concept for students to understand in order to completely understand the science of genetic engineering.

Following the Griffith experiment embedded assessment, the instructor selected student responses from the previous banana DNA experiment “Is DNA alive, why or why not,” and shared them with the class. Confronting students with their own ideas about a concept is the foundation of conceptual change theory (Hewson 1981; Gilbert and Watts 1983). Additionally, the use of elicited and interpreted student responses in instructional design is a critical step in the formative assessment cycle (Ruiz-Primo and Furtak 2007). There was a range of problematic to justified student responses included. The students were asked to respond to each of them and indicate whether they agreed/disagreed with the response and then asked to explain why.

For Brayden, this activity allowed him to replace his incorrect conception of DNA being alive with a scientifically correct conception. In responding to the following (problematic) student response “yes, DNA is alive because it is in all living things and can be extracted out and put in something else,” Brayden wrote, “disagree, DNA is just a chemical and just because it can be transferred from cell to cell does not mean it is alive.” Here, it is evident that Brayden now has the correct conception of the chemical nature of DNA. This was retained on his post-BIKE response to the question about extracting DNA from a dead frozen animal, “true, DNA is not living and can be good from any cell whether it was living or not or frozen.”

Students with a persistent problematic trend from pre- to posttest also had difficulty in responding to these embedded assessments. In fact, Alyssa’s response to the following question on the first course exam, “if a cell dies, the DNA in it loses its information. True or False. Briefly explain” was, “just like in the Griffith experiment, we see that when a cell dies, the genetic information dies as well.” This response is incorrect, and it is evident from our analysis that Alyssa not only held a persistent misconception about the chemical nature of DNA but also misinterpreted the results of an experiment that was intended to help students confront their misconceptions. Collectively, what our results demonstrate is that this concept is difficult for students, and even with targeted instruction using context-based applications, students still hold on to their prior alternative conceptions.

Discussion and Implications

Our research revealed that students have difficulty understanding the chemical nature of DNA. Understanding students’ alternative conceptions is an essential part of developing an instructional plan to promote student learning. To inform their instructional approaches, as well as to enhance student understanding and scientific literacy, college science instructors need ways to assess students’ conceptual understanding pre- and post-instruction. Pre-/posttests, like the BIKE used in this study, not only identify the types of alternative conceptions students hold but also inform educators of conceptual areas that require remedial attention and/or how to tailor appropriate teaching techniques to meet students’ needs (Heady 2004). These assessments should align with teaching practices and vary in question format (National Research Council 2001). Yet, few studies have examined the formative assess-instruct-assess cycle for in-depth learning of a science concept (Ruiz-Primo and Furtak 2007).

Our study provides a research-based example of developing strategies not only to elicit student conceptions but also how to design innovative assessments to target the alternative conceptions that are evident among students. The chemical nature of DNA is a fundamental concept in STEM fields, where crosscutting ideas are essential to enhance student learning (National Research Council 2011). To date, we are unaware of any research that has examined this concept before. In addition, we found that contextual examples are critical for students to be motivated to abandon old ideas.

When considering the chemical nature of DNA, this study investigated the use of a hands-on inquiry activity, a classical experiment using an animal model—the Griffith experiment, as well as incorporating students’ own understandings into an assessment to replace these misconceptions with scientifically acceptable conceptions (Smith et al. 1993). These activities were in addition to course instruction on DNA structure and function. Traditionally in this course context, the chemical nature of DNA was introduced through lectures. When it became clear that the students had difficulty understanding this concept, additional activities were added to the sequence of instruction. Specifically, the DNA extraction and Griffith experiment embedded assessments. However, the misconception remained with many students. We then added the incorporation of students’ own understandings of the concept into an assessment. However, 40 % of the students still retained alternative conceptions about the chemical nature of DNA post-instruction (Fig. 1). This aligns with the persistence characteristics of misconceptions as described by Smith et al. (1993).

It is unclear to us if the students who come out of the course still holding on to the misconception of DNA being alive were truly reflective in their thinking about this concept. They were introduced to the scientific way of thinking, received hands-on instruction, and were encouraged to reflect on their own understandings. Perhaps students should be made more accountable for their own understandings of this topic, and instructors should explicitly ask the students to reflect on their prior understandings in light of the scientific evidence. As Posner et al. (1982) posited, conceptions should be reasonable to the students and new conceptions should better make meaning to their experience and observations. This is particularly difficult when dealing with complex microscopic biological processes that cannot be visualized (Lawson et al. 2000). Since the study concluded, we have added explicit instruction in the question of “What is life?” to further confront student ideas surrounding this misconception.

Revealing this persistent misconception is a major contribution to teaching and learning in STEM fields. Smith et al. (1993) note that misconceptions can impede future learning. Since this concept is fundamental to fully understanding complex biological processes such as protein synthesis, heredity, and genetic engineering, future research needs to address additional ways to confront this misconception to foster a scientifically accurate understanding of this core concept.

Acknowledgments

The authors would like to thank Jill Maroo for her assistance with the statistical analysis. This material is based on work supported by the National Science Foundation (NSF) under Grant No. 0837021. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF.

Copyright information

© Springer Science+Business Media B.V. 2012