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The Comparative Effects of Prediction/

Discussion‐Based Learning Cycle,

Conceptual Change Text, and

Traditional Instructions on Student

Understanding of GeneticsDiba Yilmaz

a , Ceren Tekkaya

a & Semra Sungur

a

a Middle East Technical University, Ankara, Turkey

Published online: 24 May 2010.

To cite this article: Diba Yilmaz , Ceren Tekkaya & Semra Sungur (2011): The Comparative

Effects of Prediction/Discussion‐Based Learning Cycle, Conceptual Change Text, and Traditional

Instructions on Student Understanding of Genetics, International Journal of Science Education,

33:5, 607-628

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International Journal of Science Education

Vol. 33, No. 5, 15 March 2011, pp. 607–628

ISSN 0950-0693 (print)/ISSN 1464-5289 (online)/11/050607–22

© 2011 Taylor & Francis

DOI: 10.1080/09500691003657758

RESEARCH REPORT

The Comparative Effects of Prediction/

Discussion-Based Learning Cycle,

Conceptual Change Text, and

Traditional Instructions on Student

Understanding of Genetics

Diba Yilmaz, Ceren Tekkaya and Semra Sungur* Middle East Technical University, Ankara, Turkey

Taylor and FrancisTSED_A_466284.sgm10.1080/09500691003657758Prometheus0810-9028 (print)/1470-1030 (online)Original Article2010Taylor & Francis0000000002010Dr. SemraSungur [email protected]

The present study examined the comparative effects of a prediction/discussion-based learning

cycle, conceptual change text (CCT), and traditional instructions on students’ understanding of

genetics concepts. A quasi-experimental research design of the pre-test–post-test non-equivalentcontrol group was adopted. The three intact classes, taught by the same science teacher, were

randomly assigned as prediction/discussion-based learning cycle class ( N = 30), CCT class ( N =

25), and traditional class ( N = 26). Participants completed the genetics concept test as pre-test,

post-test, and delayed post-test to examine the effects of instructional strategies on their genetics

understanding and retention. While the dependent variable of this study was students’ understand-

ing of genetics, the independent variables were time (Time 1, Time 2, and Time 3) and mode of

instruction. The mixed between-within subjects analysis of variance revealed that students in both

prediction/discussion-based learning cycle and CCT groups understood the genetics concepts and

retained their knowledge significantly better than students in the traditional instruction group.

Keywords: Conceptual change; Experimental study; Genetics; Learning cycle; Science

education

Introduction

Considerable research in education has reported that students come to class with

varying ideas about science and the natural world (e.g. Duit & Treagust, 2003). In

*Corresponding author. Department of Elementary Education, Faculty of Education, Middle East

Technical University,[Idot]

nönü Bulvarı, Ankara 06531, Turkey. Email: [email protected]˙


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608 D. Yilmaz et al.

fact, Ausubel (1968) mentioned the importance of students’ existing knowledge in

constructing new knowledge in a meaningful way. When the students cannot

construct effective linkages between their existing knowledge and the new knowl-

edge, development of conceptions is prevented (Novak, 1988), which in turn leads

to rote learning. Genetics is among such topics that students tend to learn by rote(Cavallo, 1996). Several researchers have also shown that genetics is one of the most

important and difficult topics of science to learn (Bahar, Johnstone, & Hansell,

1999; Banet & Ayuso, 2000; Duncan & Reiser, 2007; Kindfield, 1991; Smith &

Williams, 2007; Venville & Donovan, 2007). Major concepts of genetics that the

students do not fully understand include chromosomes, genes, alleles, homozygous,

heterozygous, dominance, recessiveness, mitosis, meiosis, and fertilization (Clark &

Mathis, 2000; Lewis, Leach, & Wood-Robinson, 2000a, 2000b; Slack & Stewart,

1990). Major reasons of students’ incomplete understanding of genetics concepts lie

under the ontological differences between the levels of genetics phenomena (Duncan

& Reiser, 2007), abstract nature of concepts (Law & Lee, 2004), and relatedness of

these concepts to different levels of organizations, namely, macroscopic level (organ-

ismal), microscopic level (cellular), and submicroscopic level (biochemical), which

need connection among each other for coherent understanding (Marbach-Ad &

Stavy, 2000). Students should connect each genetics concept with each other in a

meaningful way in order to understand further scientific concepts such as reproduc-

tion, biological diversity of organisms, mutation, adaptation, evolution, and daily life

applications of genetics such as cloning, medicine, agriculture, forensic science, and

genomics (Rotbain, Marbach-Ad, & Stavy, 2006; Tsui & Treagust, 2007). More-

over, in order to be effective scientific literate citizens in the future, individualsshould have an understanding of basic concepts of genetics (Venville, Gribble, &

Donovan, 2005). Therefore, meaningful learning of genetics concepts has become

an important issue.

Researchers have offered alternative strategies to promote meaningful learning in

science. According to Novak (2002), conceptual change is a necessity for meaning-

ful learning to occur. On the basis of Piaget’s notions of assimilation, accommoda-

tion, and disequilibrium, conceptual change theory focuses on the conditions

necessary for students to modify their existing conceptions with new ones (Roth,

1985; Wang & Andre, 1991). In assimilation, students use their existing conceptswhile interpreting the new knowledge and make the new knowledge consistent with

the existing knowledge. However, in accommodation, students change and adapt

existing knowledge to be consistent with the new knowledge (Posner, Strike,

Hewson, & Gertzog, 1982). According to conceptual change theory, four condi-

tions should be met in order to promote conceptual change (Posner et al., 1982).

According to Posner et al., students must be dissatisfied with existing knowledge, the

new conception must be intelligible (the students understand the meaning of the new

concept), the new concept must be plausible (student must find it believable), and the new

concept must be fruitful (students can solve other problems using the new concept). If these

conditions are met, accommodation of the new conception may occur. There areseveral research studies that utilize different teaching strategies based on conceptual


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Conceptual Understanding in Genetics 609

change theory. Learning cycle and conceptual change texts (CCTs) are among such

strategies.

The learning cycle, derived from Piaget’s model of mental functioning, was

introduced as a part of the Science Curriculum Improvement Study to enhance

elementary school students’ concept development (Karplus, 1977). It is an inquiry-based teaching strategy and divides the instruction into three phases: exploration,

concept introduction, and concept application (Karplus, 1977; Purser & Renner,

1983; Renner, Abraham, & Birnie, 1988). For instance, the exploration phase allows

students to assimilate the essence of the science concept through direct experiences.

When students explore a new concept through an exploration, their new experiences

cause them to re-evaluate their past experiences. This produces equilibrium, and

students accommodate the concept to reach equilibration. The concept application

phase provides students with opportunities to relate the newly developed science

concept to everyday applications through a cognitive process that Piaget referred to

as organization (Marek & Cavallo, 1997; Martin, Sexton, & Gerlovich, 2001).

The learning cycle has been the centre of attention of research studies in the field

of science education for years. These studies have documented the effectiveness and

widespread applicability of the learning cycle to a variety of grade levels and to

several disciplines (Abraham & Renner, 1986; Barman, Barman, & Miller, 1996;

Cavallo & Laubach, 2001; Colburn & Clough, 1997; Lindgren & Bleicher, 2005;

Marek & Cavallo, 1997; Odom & Kelly, 2001). For example, Renner (1986)

compared the effectiveness of the learning cycle and expository instruction in

promoting gains in content achievement and intellectual development of 9th- and

10th-grade students. Results revealed that learners at the concrete level taught bythe learning cycle method made significantly greater gains on concrete concepts and

moved more often from one developmental level to another when compared to

students in the expository group. Studying with sixth-grade students, Saunders and

Shepardson (1987) explored the effects of concrete (learning cycle) and formal

(traditional) instructions on reasoning and science achievement. The authors

reported significantly higher levels of performance in science achievement and

cognitive development favouring the learning cycle instruction group. Likewise,

Marek, Cowan, and Cavallo (1994) indicated the effectiveness of learning cycle

instruction in promoting high school students’ understanding of diffusion concepts.In another study, Barman et al. (1996) compared the learning cycle teaching

approach with a textbook/demonstration method of instruction to determine

whether one method is more effective in facilitating fifth-grade students’ conceptual

change concerning sound. The findings showed that students who were taught using

the learning cycle had a statistically significant better understanding. As the learning

cycle has been used, researched, and refined over the years, different types of learn-

ing cycle have been developed. Prediction/discussion-based learning cycle (HPD-

LC) is one of the learning cycle types in which a prediction/discussion phase is

added at the beginning of three-phase learning cycle involving exploration, term

introduction, and concept application phases (Lavoie, 1999). In the prediction/discussion phase, hypothetico-predictive problem sheets are administered to the


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students in which they make predictions about the related problem and form a

hypothesis. This phase is followed by whole-class and small-group discussions in

which the students discuss their predictions and their reasons. In the exploration

phase, students explore and test their own predictions by observing and collecting

data related with the question while involved in an inquiry activity. In the term intro-duction phase, the teacher explains related terms and discusses the results obtained

in the exploration phase. In the final phase, the concept application phase, students

extend the new concept while solving problems and answering questions about it.

When compared with traditional learning cycle instruction, HPD-LC appeared to

provide significantly greater gains in using process skills, logical thinking skills,

science concepts, and scientific attitudes (Lavoie, 1999).

Besides the learning cycle approach, various text-based structures, such as CCT

and refutational texts, have been designed to help learners change their misconcep-

tions and to facilitate conceptual change (Chambers & Andre, 1997; Roth, 1985).

For example, in one of her earlier studies, Roth adapted Posner et al.’s (1982) model

to middle-grade science instruction on photosynthesis to shed more light on

students’ difficulties in learning science from textbooks. Roth, in designing her

‘experimental text’, first identified students’ common misconceptions about photo-

synthesis and plant food. The experimental text posed questions, such as ‘how do

you think plants get their food?’, to elicit students’ misconceptions. The text then

emphasized the conflicts between students’ misconceptions and scientifically

accepted conceptions. Next, it explicitly challenged students’ misconceptions about

food for plants by presenting evidence to challenge students’ misconceptions and

convince them that the substances they usually describe as food for plants are notfood in a typical scientific sense. After providing the scientifically correct explana-

tion, the text presented reviews of the important concepts and application questions

that require students to apply new concepts to a variety of situations. Roth’s study

(1985) indicated that students who were instructed using an experimental approach

outperformed those who were instructed using a traditional approach. Roth

concluded that the text structure, which meets each of the four criteria for concep-

tual change learning in Posner et al.’s model (1982), helps students use a conceptual

change approach while reading the text. Roth’s study suggested that ‘knowledge

about common students’ misconceptions can be used to write texts that challengestudents’ misconceptions and help them see how these misconceptions are in

conflict with scientific explanations of phenomena’ (p. 35). She also pointed out that

the conceptual change strategy helps students be aware of their pre-knowledge, real-

ize the inconsistencies between scientific ideas presented in the text and their naive

ideas, and use this knowledge to explain the everyday phenomena.

By using Posner et al.’s (1982) and Roth’s (1985) conceptual change model,

Wang and Andre (1991) designed the so-called ‘conceptual change text’ to find out

whether the text would promote development of more mature conceptual under-

standings of direct current. They prepared a CCT by following a set of guidelines:

(1) involving the determination of typical student misconceptions about a topic, (2)eliciting students’ misconceptions through presenting simple examples that leads


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students to use their misconceptions to make a prediction about the situations, (3)

providing evidence that the common misconceptions were wrong, (4) presenting

scientifically accepted ideas, and finally (5) providing students with an opportunity

to apply scientifically correct ideas via adjunct questions. Similar to Roth’s finding

(1985), Wang and Andre (1991) reported that CCT produced better acquisition of the concepts compared with traditional text.

To summarize, in the CCT, students are asked explicitly to predict what would

happen in a situation before being presented with information that demonstrates the

inconsistency between common misconceptions and the scientific conceptions. The

aim is to activate students’ misconceptions by posing questions and presenting

common misconceptions. Once students’ misconceptions are activated, disequilib-

rium between students’ existing conceptions and the scientific conception can be

created. Then, scientific explanations that are supported by examples are provided.

Several studies showed that CCTs are effective in creating conceptual change and

leading to meaningful learning of many science concepts (e.g. Chambers & Andre,

1997; Mikkila, 2001; Roth, 1985; Wang & Andre, 1991).

Another text structure based on Posner et al.’s (1982) conceptual change model is

the refutational text (Alvermann & Hynd, 1989; Diakidoy, Kendeou, & Ioannides,

2003; Guzzetti, 2000; Guzzetti, Williams, Skeels, & Wu, 1997; Hynd, 2001;

Palmer, 2003). Refutational text is defined as a text that states students’ existing

misconceptions and directly refutes them while providing the scientifically correct

explanation (Guzzetti, 2000; Guzzetti et al., 1997). According to Dole (2000),

recognizing students’ misconceptions and refuting them can encourage students to

become dissatisfied with their prior knowledge. Next, the text provides plausible alter-natives to encourage students to attend to the new information and restructure their

knowledge based on that information.

As stated by Chambers and Andre (1997), the main distinction between the refu-

tational text and CCT involves whether students are asked explicitly to make a

prediction about a situation. In the refutational text, common misconceptions are

contrasted to scientific conceptions, but the student is not asked first to make a

prediction about a common situation before the refutation is given. In the CCT

model, however, students are asked explicitly to make a prediction about what

would happen in a situation before being presented with information that demon-strates the inconsistency between the common misconceptions and the scientific

conceptions. Following the prediction phase, the students are presented with

common misconceptions along with the evidence countering these misconceptions.

Both instructional strategies, however, are in line with the constructivist approach in

which students’ knowledge is taken into consideration. On the other hand, compara-

tive effects of these strategies on students’ understanding of science concepts,

including genetics, have not been well documented. In the present study, students’

understanding of genetics was examined due to its curricular significance. It is a core

concept in the science curriculum and considered to be an abstract and difficult

topic for the students to learn. While some research focuses on the difficulties inteaching and learning genetics, other examines students’ conceptions related to


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science lessons were offered as three 40-minute periods per week. The treatment,

thus, consisted of a total of 600 minutes of instruction. This time period does not

include administrations of pre, post, and delayed post-tests.

Instruments

The data were collected in this study through GCT.

The genetics concept test. The GCT was developed by the first author to determine

students’ conceptual understanding of genetics concepts by examining the related

literature (e.g. Cavallo, 1996; Lewis & Wood-Robinson, 2000; Lewis et al., 2000a,

2000b; Sampson, 2002) and the objectives related to the genetics unit determined

by the national science curriculum. The test assesses students’ understanding of

basic concepts of genetics, namely, basic terminology of genetics, Mendelian genet-

ics, inheritance, and genetics crosses (see Appendix A). It consists of 15 multiple-

choice items, with one correct answer and three distracters. The distracters of some

items were adapted from the above-mentioned published works. Content validity of

each item in the test was determined by experts in biology education and one

research assistant. The science teacher also analyzed the relatedness of the test items

to the instructional objectives. The panel members confirmed that the content valid-

ity of the instrument was appropriate for the participants and determined that the

GCT was valid with respect to the constructs measured.

The GCT, after pilot testing, was administered to students in each group as a pre-test, post-test, and delayed post-test to assess the change in students’ understanding

of genetics concepts over time. One class hour was devoted to each testing proce-

dure. The reliability coefficient was found to be 0.73 by using Kuder–Richardson

Formula 20.

Treatment

Prediction/discussion-based learning cycle instruction. In this study, two separate HPD-

LC lessons, one for the basic terminology of genetics and passing of traits and theother for Mendelian genetics and genetics crosses, were developed by focusing on

objectives of the lesson. Lesson plans, including the objectives and detailed explana-

tions of each phase of the HPD-LC, were prepared as a guide. For example, in the

prediction/discussion phase of the learning cycle activity concerning passing of traits,

hypothetico-predictive problem sheets, which required students to individually make

predictions about passage of traits from parents to offspring, were distributed to the

students. In this worksheet, students were asked to use the photographs of different

species of dogs and puppies to predict which dogs were the members of the same

family. They were also asked to predict the reason why puppies look similar to their

parents. The aim of this question was to determine the students’ prior understand-ing about how and why offspring resemble their parents. Once they had completed


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Traditional Instruction

Students in the control group received TI, which was based on lecture and discus-

sion/questioning methods. The teaching strategy mainly relied on explanation by the

teacher. The teacher explained the concepts by drawing examples on the board and

illustrating important facts in the order as it appeared in the textbook. Specifically,

the teacher used the chalkboard to write notes about the definitions of concepts, such

as phenotype, genotype, heterozygous, and homozygous, and drew figures related to

genetic crosses. After the teacher’s explanation, concepts were discussed by teacher-

directed questions. The remaining time was taken up with the solving of various

problems. The lesson ended with the students answering the questions orally. The

main idea behind this teacher-centred instruction was to provide students with clear

and detailed information. Students appeared to play a fairly passive role. Such

instruction did not take students’ misconceptions into account. On the other hand,

CCT instruction focused on teacher–student and student–student interaction,supporting a change in students from passively receiving information to actively

examining their own concepts. In CCT instruction, the emphasis was placed on

students’ pre-knowledge and misconceptions as well (see Appendix B).

Analysis of Data

A mixed between-within subjects’ analysis of variance (ANOVA) was used to inves-

tigate the effects of the HPD-LC instruction, CCT instruction, and TI on students’

genetics understanding and to determine whether there was a change in students’understanding of genetics across the three time periods: before the instruction (Time

1), after the instruction (Time 2), and one month after the instruction (Time 3).

Results

Descriptive statistics concerning the variables of the study were presented in Table 1.

The table revealed that whereas HPD-LC students appeared to have the highest mean

score, TI students had the highest gain score across time (T1, T2, and T3). Moreover,

when the mean scores for both before and after the instruction were examined, it was

found that there was an increase in the mean scores for all instructional modes. The

results showed that retention on the GCT was the lowest for the T1 students one

month after the instruction.

A mixed between-within subjects’ ANOVA was conducted to compare the effec-

tiveness of HPD-LC instruction, CCT instruction, and TI on understanding of

genetics-related concepts and to examine the changes, if any, in students’ genetics

understanding before the instruction, after the instruction, and one month after the

instruction. A mixed between-within subjects’ ANOVA was followed by the multiple

comparisons of simple main effects that controlled for pre-existing differences

among the treatment groups, to determine the effect of different instructional modeson students’ understanding across time.


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T a b l e 1 . D

e s c r i p t i v e s t a t i s t i c s

P r e - G

C T ( T 1 )

( N = 8 1 )

P o s t - G

C T

( T 2 ) ( N = 8 1 )

D e l a y e d p o

s t -

G C T ( T 3

)

( N = 8 1 )

G a i n s c o r e 1 p o s t –

p r e - G

C T

( N = 8 1 )

G a i n S c o r e 2 D e l a y e d

p o s t – p o s t - G

C T

( N = 8 1 )

G a i n S c o

r e 3 D e l a y e d

p o s t –

p r e - G

C T

( N

= 8 1 )

M o d e o f i n s t r u c t i o n

M e a n

S D

M e a n

S D

M e a n

S

D

M e a n

S D

M e a n

S D

M e a n

S D

H P D

- L C

6 . 7

7

2 . 4

9

9 . 6

0

3 . 2

0

9 . 9

0

3 . 1

7

2 . 8

3

3 . 5

1

0 . 3

0

3 . 2

1

3 . 1

3

2 . 7

3

C C T

3 . 7

6

2 . 5

4

8 . 3

2

2 . 5

6

9 . 3

2

2 . 7

3

4 . 5

6

2 . 6

8

1 . 0

0

3 . 7

1

5 . 5

6

4 . 2

7

T I

3 . 5

4

2 . 0

0

6 . 1

5

2 . 1

3

5 . 7

7

2 . 5

7

2 . 6

2

2 . 7

9

− 0 . 3

8

2 . 6

7

2 . 2

3

3 . 3

5

T o t a l

4 . 8

0

2 . 7

8

8 . 1

0

3 . 0

3

8 . 4

0

3 . 3

6

3 . 3

0

3 . 1

3

0 . 3

0

3 . 2

2

3 . 5

9

3 . 6

9


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Before conducting the analysis, assumptions of mixed between-within subjects’

ANOVA were checked. Skewness and kurtosis values were examined in order to check

normality. Skewness and kurtosis values of around 1.00 indicated that the scores were

normally distributed. Moreover, the result of Box’s M test revealed that homogeneity

of intercorrelations’ assumption was met, F (12, 27922) = 1.85, p = 0.035 ( p > 0.001).In addition, Levene’s test of equality of error variances indicated that variances of the

dependent variable were equal across all groups ( p > 0.05).

After checking the assumptions, a mixed between-within subjects’ ANOVA was

conducted. The results indicated that there was a statistically significant interaction

effect between time and mode of instruction, Wilks’ lambda = 0.85, F (4, 154) = 3.19,

p = 0.01 and η2 = 0.08. The statistically significant interaction means that differences

across time are not consistent among students exposed to different modes of

instruction.

As can be inferred from Table 1, HPD-LC students had the highest mean score,

whereas TI students had the lowest mean score across time. Although the mean

scores for CCT and TI students were comparable before the instruction (Time 1), a

large difference in the mean scores in favor of CCT students was observed after

the instruction (Time 2). This difference became more apparent one month after the

instruction (Time 3). These results suggested that CCT students were better in the

understanding and the retention of genetics concepts compared with TI students.

On the other hand, retention was better for the HPD-LC students whose genetics

understanding was also better compared with CCT and TI students both before and

after the instruction.

In order to determine whether the observed differences in means were statisticallysignificant, multiple comparisons of simple main effects for mode of instruction were

examined (see Table 2).

Table 2. Multiple comparisons of genetics understanding by mode of instruction across time

Comparison Mean difference p

HPD-LC

Time 1 vs. Time 2NN −

2.83*

0.000Time 1 vs. Time 3 −3.13* 0.000

Time 2 vs. Time 3 −0.30 1.000

CCT

Time 1 vs. Time 2 −2.62* 0.000

Time 1 vs. Time 3 −2.23* 0.005

Time 2 vs. Time 3 0.39 1.000

TI

Time 1 vs. Time 2 −4.56* 0.000

Time 1 vs. Time 3 −5.56* 0.000

Time 2 vs. Time 3 −1.00 0.372

* p < 0.05, where p values are adjusted using the Bonferroni method.


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The results presented in Table 2 revealed that there was a significant improvement

in genetics understanding from pre-test (Time 1) to post-test (Time 2), and from pre-

test (Time 1) to delayed post-test (Time 3) across all instructional modes. However,

the improvement from post-test (Time 2) and delayed post-test (Time 3) was non-

significant for all instructional modes. In addition, the gain scores showed that whilethe improvement was better for CCT students compared with HPD-LC and TI

students, the least gain was obtained by TI students. A mixed between-within

subjects’ ANOVA conducted on the gain scores, on the other hand, revealed that the

observed difference in the gain scores in favor of CCT students was statistically signif-

icant only for Time 3–Time 1 gain scores ( p < 0.05). Moreover, it was found that for

all instructional groups, the Time 3–Time 2 gain score was significantly better than

the Time 2–Time 1 and the Time 3–Time 1 gain scores ( p < 0.05).

When the proportion of correct responses determined by the item analysis for each

instructional group was examined for post-GCT, striking differences among the

groups in favor of the HPD-LC instruction and CCT instruction on several items

were indicated. For example, one such item was related to Punnett square. In this

item, students were asked to find the parents’ genotypes by using children’s genotypes

given in a Punnett square. The proportions of correct responses of the students in

HPD-LC, CCT, and TI classrooms for this item were 76.7%, 76.0%, and 38.5%,

respectively. Another item dealt with monohybrid crosses and pedigrees. The propor-

tions of correct responses of students instructed with HPD-LC, CCT, and TI were

70%, 64.0%, and 19.2%, respectively. The next item assessed the probability

concept. Students were asked to calculate the probability of an offspring having black

hair. The proportions of correct responses of students who received HPD-LCI,CCTI, and TI for this question were 80.0%, 72.0%, and 38.5%, respectively. In

another item, students were asked the number of offspring who are heterozygous for

hair colour. The proportions of correct responses of students who received HPD-

LCI, CCTI, and TI for this question were 86.7%, 80.0%, and 46.2%, respectively.

Similarly, experimental group students were also found to be more successful on a

knowledge-level item (Item 1) related to location of genes than the students in the

control group. While over 90% of the experimental group students responded to this

item correctly, the corresponding percentage for the control group students was 61.5.

In general, the present study revealed that both HPD-LC and CCT instructionsproduced significantly greater understanding of genetics-related concepts and

retention of knowledge compared with the TI students.

Discussion

The present study compared the effectiveness of HPD-LC instruction, CCT

instruction, and TI on eighth-grade students’ understanding of basic concepts of

genetics.

In the light of the results, it can be concluded that HPD-LC and CCT instruc-

tions promoted better understanding and retention of the genetics conceptscompared with the TI. For the HPD-LC instruction, this finding can be attributed


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to several reasons. First, the problem sheets were designed to elicit students’ pre-

existing conceptions, encouraging them to formulate their own hypothesis during

the exploration phase, which may have led to more meaningful learning. Second,

students were actively involved in the learning process and constructed their own

knowledge while manipulating, observing, and recording the data and testing theirown hypothesis during exploration phase, which may have led to meaningful learn-

ing. Third, as it was mentioned in the literature review part, in order for the students

to understand genetics concepts coherently, they should form effective linkages

among these concepts. Actually, the interrelated phases of the HPD-LC were

designed to help students relate the newly learned concepts with each other and with

the existing ones. While understanding the new knowledge, these students were

expected to think about their existing knowledge and reflect on them. Fourth,

during the concept application phase, students were able to extend their newly

constructed knowledge by applying them to new situations. Finally, the teacher

guided whole-class and small-group discussions after the prediction/discussion

phase and during the exploration phase.

In addition, findings regarding the effectiveness of CCT instruction can be

explained as follows. In CCT class, CCTs were designed according to Posner et al.’s

(1982) four conditions: dissatisfaction, intelligibility, plausibility, and fruitfulness.

Students in CCT instruction were involved in activities that helped them revise their

prior knowledge and struggle with their misconceptions. For instance, in the CCTs,

emphasis was given to students’ misconceptions. To deal with these misconceptions,

students first became dissatisfied with their existing conceptions, which let them

accept better explanations to the problems that were introduced. In this way,students were encouraged to think about their own pre-existing knowledge and

reflect on it. In fact, the essential component of the CCT was the social interaction

provided by teacher-guided discussions that helped students share their own ideas

and ponder them deeply. Such instruction involved intensive teacher–student inter-

action. Discussion of the concepts present in the texts could facilitate students’

understanding as well as encourage their conceptual restructuring for the further

intension of persuading students that the scientifically acceptable new conception

was more meaningful. Teaching for conceptual change, thus, required a teaching

strategy in which students had enough time to identify and express their concep-tions, examine the soundness and utility of their current ideas and those of others,

and apply new ideas in a context familiar to them.

However, the present study revealed that students still had difficulty in sound

understanding of concepts of genes and alleles even after the HPD-LC and CCT

instructions. For example, in an item dealing with Mendel’s genetic crosses, less

than 10% of students responded to the question correctly. This result further

supports the evidence that gene and alleles remain to be the most difficult concepts

for students to understand even with an instruction designed to address them.

These findings are consistent with the numerous studies investigating the effective-

ness of the learning cycle (e.g. Barman et al., 1996; Lavoie, 1999; Marek et al., 1994;Schneider & Renner, 1980) and conceptual text instruction (e.g. Chambers & Andre,


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1997; Wang & Andre, 1991) over TI. For example, in a study (Lavoie, 1999)

comparing the effects of HPD-LC and a traditional learning cycle, HPD-LC was

found to be more effective than the traditional learning cycle in improving conceptual

understanding. Authors of the study suggested that integration of the prediction/

discussion phase allowed students to test their own predictions and become aware of the changes in their own conceptions. This phase also promoted the teacher’s aware-

ness of students’ preconceptions. Prior research also emphasized the relationship

between Piaget’s model of mental functioning and the learning cycle (e.g. Abraham

& Renner, 1986; Marek & Cavallo, 1997). In fact, the exploration phase of the learn-

ing cycle, which allows students to experience the new concept, is expected to

promote assimilation. During assimilation, disequilibrium can also occur, as students

use their existing conceptions while exploring the new concept. Supporting this idea,

Marek and Cavallo (1997) mentioned that assimilation and disequilibrium can be

fostered by the use of the exploration phase. When the disequilibrium occurs,

students need to construct new mental structures to reach equilibrium during the

second phase, term introduction, and this corresponds to accommodation. In the last

phase of the learning cycle, concept application, the instruction was designed to

encourage students to extend their new concepts by applying them in other situations,

and this phase matches with the process of organization. Additionally, whole-class

and small-group discussions were designed to help students become aware of other

students’ conceptions and encourage students to verify whether their own concep-

tions were correct. Student interaction during group work is also important.

Limitations of the Study

There are some limitations that should be considered for further studies. In the

present study, the sample size of each instructional group was small, ranging from

25 to 30. In the experimental studies, in order to improve the representativeness

of the sample, it is recommended that at least 30 participants are involved in each

group (Fraenkel & Wallen, 2006). Moreover, although the three different types of

instruction were clearly described and planned out in detail in the current study,

the degree to which the teacher adhered to the exact treatment designs on a daily

basis is not known. Another limitation is that the test was given multiple times,and there could have been a testing effect that influenced the results. In addition,

in the current study, a multiple-choice test was used to assess students’ under-

standing of the instructed concepts. However, such a test may not be sufficient to

distinguish whether conceptual change occurred in terms of accommodation or

assimilation of information into students’ already existing schema. Furthermore,

the multiple-choice test administered in the study was not designed specifically to

diagnose students’ misconceptions. Therefore, it may not provide a clear picture

of students’ misconceptions. For this reason, in the future studies, different

assessment techniques, such as diagnostic tests (e.g. Odom & Barrow, 1995),

concept maps, and face-to-face interviews, can be used to reveal deep conceptualelaborations.


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Educational Implications

A number of implications emerged from the findings of the present study for science

teachers, researchers, and curriculum developers. HPD-LC instruction and CCT

instruction were found to be more effective in helping students acquire and retain

genetics concepts than TI. Therefore, it is suggested that instructional strategies,

which take into consideration students’ pre-existing knowledge and encourage

students to be active participants both physically and mentally in the learning process,

should be integrated into curriculum. Students were given opportunities to test their

own ideas and work collaboratively with peers in order to increase their science

achievements. To this end, pre-service and in-service science teachers should be

informed about the usage, integration, and importance of such strategies. Curriculum

developers should also consider these teaching strategies while developing new science

curricula in order to increase students’ achievement in science learning.

All together, findings of the present study indicated that when students receivedappropriate instruction in helping them to understand relevant ideas, sound under-

standing of genetics concepts could be achieved. The findings suggest the use of

HPD-LC and CCT instructions as alternatives to TI to enhance students’ genetics

understanding and retention.

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Appendix A. Genetics Concept Test

1. Where, in your body, are genes found?

(A) in the reproductive system

(B) in all cells

(C) in the nucleus

(D) in the chromosomes

2. Which one of the following explanations related with alleles and genes is TRUE?

(A) Genes contain alleles.

(B) Allele is a particular form of a gene.

(C) Genes and alleles are the same.

(D) Alleles contain genes.

3. Which of the following statements is TRUE?

(A) Most traits are controlled by one gene pair.(B) Every trait is controlled by a single gene.

(C) Most traits are controlled by 23 genes.

(D) Every trait is controlled by 46 genes.

4. If a couple had three daughters in a row, what is the probability that the fourth

child would be male?

(A) 1/2 (B) 1/3 (C) 1/4 (D) 2/3

5. In pea plants, purple-flowered is dominant over white-flowered. If a purple-

coloured flower (heterozygous; Bb) were crossed with a white-flowered

(homozygous; bb) pea plant, what would be the possible phenotypes of the

offspring?

(A) 100 % purple flowered

(B) 75% purple flowered, 25% white flowered

(C) 50% purple flowered, 50% white flowered

(D) 25% purple flowered, 75% white flowered

6. Which one of the following explanations related with cells of skin, muscle, and

bone from the same individual is TRUE?

(A) All cells contain the same genetic information.

(B) All cells contain the different genetic information.

(C) Skin cells carry the different genetic information.

(D) Muscle cells do not carry the same genetic information as skin and bone

cells.

7. The genotypes of three individuals are provided below. Which individuals do

you think have the same phenotypes?

Individual 1: Aa

Individual 2: AA

Individual 3: aa(A) 1, 2, and 3 (B) 2 and 3 (C) 1 and 3 (D) 1 and 2


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8. In peas, round seed (H) is dominant to wrinkled seed (h). Which of the follow-

ing crosses yielded 1/2 wrinkled and 1/2 round offspring?

(A) HH × hh (B) Hh × hh (C) Hh × Hh (D) hh × hh

9. As it is shown in the pedigree given on the right, Susan and Dennis have two

daughters named as Selma and Karen. Selma has blue eyes and Karen has black

eyes. Which one of the following conclusions cannot be drawn from this infor-

mation? (Black eyes is dominant over blue eye)

(A) Susan is homozygous.

(B) Dennis has black eyes.

(C) Selma may have blue eyes.

(D) Karen is homozygous for black eyes.

10. Which one of the following conclusions cannot be drawn from results of

Mendel’s experiments?

(A) Each allele may mask the expression of other allele.

(B) Each pair of allele segregates during the gamete formation.

(C) Gametes carry both of the allele pair.

(D) Alleles of different traits assort independently of each other.

11. Using the information given in the Punnet square, determine the genotypes of the two parents.

(A) EE × ee (B) EE × EE

(C) Ee × Ee (D) Ee × ee

12. A heterozygous yellow-seeded pea plant was crossed with a pea plant of the

same genotype and produced 112 offspring. What fraction of the offspring

should have green seeds? (Recall, the allele for yellow seed is dominant and the

allele for green seed is recessive)

(A) 0 (B) 28 (C) 84 (D) 112

Direction: Questions 13–15 refer to the information and the Punnet square givenbelow.


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In human beings, the allele for black hair colour (B) is dominant and the allele for

blond hair colour is recessive (b). A man and woman are heterozygous for black hair.

The predictions for hair colour that could result in the offspring of these two parents

are presented in the Punnet square diagram below.

13. What percentage of the offspring will inherit black hair?(A) 0% (B) 25% (C) 50 % (D) 75%

14. How many offspring are expected to be heterozygous?

(A) 1 (B) 2 (C) 3 (D) 4

15. What is the ratio of black to blond hair offspring?

(A) 1/1 (B) 1/3 (C) 3/1 (D) 4/1


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Appendix B

Comparison of Instructional Methods

Conceptual Change Text Instruction

HPD-LC instruction: basic terminology of genetics and passing of traits

Prediction/discussion phase Hypothetico-predictive problem sheets were administered that

required students to individually make predictions about passage

of traits from parents to offspring. Once they had completed the

hypothetico-predictive problem sheet, the teacher initiated a

whole-class discussion in which students were encouraged to

discuss their predictions and reasons.

Exploration phase Students explored and tested their own predictions that they

made in the prediction/discussion phase. They worked in groups

to visualize the passage of traits from parents to offspring while

performing a hands-on activity.

Term introduction phase The teacher introduced basic terminology of genetics, namely,

gene, dominant allele, recessive allele, homozygous,

heterozygous, genotype, and phenotype, and discussed the results

collected in the exploration phase.

Concept application phase Students worked in groups and participated in another hands-on

activity in which they extended the concepts that were identified

in the previous phase.

The teacher distributed the texts to the students before the instruction.

The teacher directed the students to read it before the class hour and bring it to the class.

Students were informed about the new instruction, the nature of the CCT, and how they would

use it during the instruction.

Students read a paragraph in which a question was posed to arouse students’ interest in the

subject and to analyze their pre-conceptions.

Students shared their ideas about the answer with the class. The teacher did not intervene and

did not give any feedback during this process.

Typical misconceptions about the concept that were provided in the text were read aloud by

one of the students.

Students were asked to compare their conceptions with these misconceptions.

The scientifically correct explanation of the concept was provided to guide students in

considering why the misconceptions could be wrong.

The teacher asked whether anything related with the explanation surprised the students to help

the students reconstruct the concepts.

Images, figures, and pictures were used to help students visualize the concepts while reading the

text.

In addition, the history of science, such as Mendel’s life and his studies with pea plants, and the

history of Punnett square were provided.


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Traditional Instruction

Teaching strategy relied on teacher’s explanation. The teacher used the chalkboard to write

notes about the definitions of the concepts, such as; phenotype, genotype, heterozygous, and

homozygous, and to draw figures related with genetic crosses.

After the teacher’s explanation, concepts were discussed by teacher-directed questions.

The focus of the instruction was on problems related with Mendelian genetics.

No experiments or hands-on activities were performed by the students related with the topics.

Students’ prior conceptions were not taken into consideration.

The majority of instruction time was devoted to the teacher’s explanation and answering

teacher-directed questions.

Documents

The Comparative Effects of PredictionDiscussion-Based Learning Cycl.pdf