Proceedings of the 3rd International Conference of Teaching and Learning (ICTL 2011)
INTI International University, Malaysia
ASSESSING UNDERSTANDING OF BASIC GENETIC
CONCEPTS AMONG MALAYSIAN PRE-UNIVERSITY
STUDENTS AND BIOLOGY UNDERGRADUATES
Geeta, S.1 and Choo, L.S.2
INTI International University, Malaysia
(1geeta.selvarajah@newinti.edu.my, 2leesshian.choo@newinti.edu.my)
ABSTRACT
Given the importance of genetic concepts in biology, it is important to know how well students understand these
concepts. The absence or alternate understanding of basic genetic concepts is a hurdle to reasoning and higher
order understanding in molecular biology. Teachers if made aware of this can design instructional interventions.
Consequently, we examined pre-university students’ and biotechnology undergraduates; understanding of some
concepts central to the discipline, i.e. the understanding of genes, alleles, sister chromatids, homologous
chromosomes, deoxyribonucleic acid (DNA), haploid, and diploid. Utilizing a multiple-choice assessment
instrument and focus group discussion, we found that absence of or alternate understanding of these key
concepts, is present in both groups of Malaysian students. In addition we elicited student held ideas. These
findings suggest that targeted teaching of these concepts have to be mobilized.
KEYWORDS
Alternate conceptions, genetics, genes, alleles, homologous chromosomes, chromatids, DNA, haploid, diploid
INTRODUCTION
Schulman (1986) distinguished between subject-matter knowledge versus knowledge and
understanding of how the topics are understood – or misunderstood – by people stressing that
both are of vital importance for educators. Students with ideas not congruent with scientists
ideas on basic genetics concepts will find it a hindrance to understand higher level genetics
concepts and thus will resort to rote learning without understanding, just to pass exams.
Teachers if aware of these conceptual hurdles can target their teaching activities to try and
overcome them.
Thus this project aims to explore the following questions:
1. Does the inability to understand or does an alternate understanding of key genetic concepts
exist among Biotechnology undergraduates and A-level students in a Malaysian University?
2. What are students’ understandings of the following?
a. gene and allele,
b. sister chromatids and homologous chromosomes,
c. chromosomes and DNA,
d. haploid and diploid?
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Proceedings of the 3rd International Conference of Teaching and Learning (ICTL 2011)
INTI International University, Malaysia
METHOD
To answer the questions of the present study, both qualitative and quantitative research
methods are used.
Subjects
A-level science students and second year undergraduates (Biology) in a Malaysian University
were the respondents in the study, and signed informed consent forms. There were 154 and
99 A level respondents in the pre and post instruction assessment respectively. The
biotechnology group respondents comprised of 71 and, 17 undergraduates in the pre and post
instruction assessment respectively. Pressure of upcoming exams and time constraints
prevented us from interviewing A-level students. However, 17 undergraduates discussed their
answers and gave their reasons for them, in groups of 3 to 6 students.
The Instrument
The concepts tested were guided by literature and our own experience. These concepts are
covered by the secondary or high school syllabus. Comparison with other available
instruments showed limited overlap (Elrod, 2007; Smith et al., 2008; Bowling et al., 2008;
Tsui & Tregast, 2009). To prevent fatigue in answering too many questions, yet confirming
our findings with multiple questions for a single concept we compromised on an instrument
comprising eight concepts with five questions per concept. Multiple choice questions were
used based on its advantage of ease of grading, perceived objectivity, respondents feedback
unhampered by lack of erudition, and ease of administration. Most items of the instrument
surpass the recall level of knowledge, and used distracters. The questions were presented
randomly, to prevent students from linking questions to concept from the arrangement and
substance of the questions. We had modified contents based on a pilot study.
Administration of Questionnaire
Students took the multiple choice test as a one hour survey on paper during class time. They
answered the questions pre- and post instruction.
Focus Group Discussion
Focus groups discussion helped ensure common understanding of the questions between
researcher and student, and further clarify student reasoning for selecting an answer,
indicating that the responses reflect beliefs as opposed to random responses. Discussion was
based on student responses to the pre and post instruction questionnaire.
Independent Reviewers
We also established a table listing concepts being tested with the corresponding questions,
and sent it to three reviewers in the field of biology to ensure content validity.
Statistical Analysis
The assessment instrument was evaluated for validity and reliability using item difficulty,
item discrimination, point biserial coefficient, and the Kruder Richardson-20 (KR-20) value
using Test Analysis Program (TAPS; Version 2007a). Pre-and post instruction differences
were tested for significance using the Wilcoxan signed rank test. (SPSS Version 17)
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Proceedings of the 3rd International Conference of Teaching and Learning (ICTL 2011)
INTI International University, Malaysia
RESULTS & DISCUSSION
Validity & Reliability of the Assessment Instrument
The three reviewers generally confirmed that for the questions tested the achievement of the
specified content area, were scientifically accurate and were written clearly. They provided
feedback, giving credence to content validity. Among the comments, one review mentioned
that one question did not address the gene-allele concept. However, since the other two
reviewers did not raise objections to the question, we decided to retain it.
Another comment by one reviewer was of the similarity of the following two questions.
1. How many chromatids are present in this
cell?
A. 6
B. 12
C. 24
D. 48
E. None of the above
4. The figure at right shows
A. a pair of homologous chromosomes
B. a pair of sister chromatids
C. a pair of gametes
D. two alleles
E. two genes
While we don’t dispute this, we decided to retain both questions in the assessment
questionnaire. The results revealed that a student’s choice of the correct option in one
question did not necessarily result in a correct choice of response in the other (for example
31% among A-level students pre-instruction). This supports reports of inconsistent student
responses to a series of questions testing the same idea (Palmer, 1992) and students holding
on to more than one concept (Tsui & Treagust, 2007). It may thus explain low correlation
amongst items testing the same concept, low point biserial correlation and KR20 values.
The point biserial coefficient and the K20 values were both on average within the acceptable
values (Table 1) indicating that the items and instrument were generally reliable and results
reproducible. Item difficulty (the proportion of students answering the item correctly) and
item discrimination (the instruments ability to discriminate between high and low
performers), were also in general within the acceptable range (Table 1), thus supporting
validity.
Table 1. Evaluation statistics of the assessment instrument compared to desired values.
Test Statistics
Our Test Instrument Values
Item Difficulty
Average values ranging from
0.37- 0.56
Average values ranging from
0.24- 0.49
Average values ranging from
0.23- 0.47
0.54- 0.92
Item Discrimination
Point Biserial Correlation
KR20 (alpha)
Desired Values
Ding & Beichner (2009)
0.3-0.9
>0.3
>0.2
>0.7
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Proceedings of the 3rd International Conference of Teaching and Learning (ICTL 2011)
INTI International University, Malaysia
Findings of this instrument corroborated and elaborated using focus group discussions, are
presented below for each concept.
Student Understanding of the Gene-Allele Concept
Every question on the gene and allele concept had a high percentage of incorrect responses
(Figure 1), both by A-level students and undergraduates substantiating the difficulty students’
face in this concept as previously documented (Pashley, 1994; Marbach-Ad, 2001; Lewis &
Kattmann, 2004; Elrod, 2008).
Figure 1. Responses to questions testing gene-allele understanding among A-level students
and biology undergraduates (Pre instruction)
The incorrect answers verified by the focus groups demonstrate student ideas listed below;
 A gene is an inherited character of an organism.
 A gene is a type of allele.
 A gene is a chromatid.
 There is no difference in saying that the gene caused the disease and the allele caused
the disease.
 A person with a disease has a gene which healthy individuals lack.
 Alleles occupy two different loci on the chromosome.
 Alleles are not formed as a result of mutation.
Students summed it up by saying they were confused by the terms gene and allele. The
confusion has been reported to lie in the incorrect use of the terms ‘gene’ and ‘allele’, being
used as synonyms in textbooks and by teachers (Cho et al., 1985). We found such instances,
for example, as stated in the text book Biology Key Ideas 2nd edition, (Crierie & Greig,
2000),
Haemophilia is a genetic disorder where those afflicted bleed excessively when
injured as they have inherited an abnormal gene involved in the process of blood
clotting.
It would be less confusing to students if the term mutant allele in place of an abnormal gene
in used.
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Proceedings of the 3rd International Conference of Teaching and Learning (ICTL 2011)
INTI International University, Malaysia
We postulate further that misconceptions also arise because textbooks and teachers fail to
mention how genes are named. Where a gene is known only by mutant phenotype, the gene is
given the name and symbol of the mutant, for example breast cancer gene (BRCA2). Thus
students mistakenly believe that the breast cancer gene will only be present in people having
the disease. What is true is that we all have the breast cancer gene, but it is only a person with
a variant of this gene, i.e. a particular allele that has a predisposition of getting breast cancer.
We suggest that authors of text books or teachers should explicitly mention this aspect on the
naming of genes.
Students’ incorrect answers to Question 37 where letter symbols depict gene and alleles in
some instances arise as mentioned (Thomson & Stewart, 1985) because students lack the
understanding of how the symbols are related to the concepts
Student Understanding of the Chromatid- Homologous Chromosome Concept
The chromatid-homologous chromosome confusion detected in the assessment (Figure 2) was
further confirmed by focus group discussion which indicated that students thought that;
 The double stranded or replicated form of a chromosome is a pair of homologous
chromosomes.
 DNA replication leads to the production of homologous chromosomes.
 The replicated or double stranded form of a chromosome is a single chromatid.
 Homologous chromosomes are present in gametes.
 Homologous chromosomes pair during prophase II.
Figure 2. Responses to questions testing chromatid-homologous chromsome concept
understanding among A-level students and biology undergraduates. (Pre-instruction)
Malaysian students’ difficulty in differentiating chromatids from chromosomes, or replicated
chromosomes with unreplicated chromosomes, is also common to students elsewhere
(Kindfield, 1994; Clark & Mathis 2000; Elrod, 2008). It has been postulated that the
similarity between the terms chromosome and chromatid lead to difficulties (Hernendez,
1993; Kindfield, 1994), which though not mentioned by the 17 students we interviewed may
exist amongst other students.
Our focus group discussion, lead us to believe that one form of fallacious reasoning behind
this confusion was that replication leads to two, so the pair of homologous chromosomes
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Proceedings of the 3rd International Conference of Teaching and Learning (ICTL 2011)
INTI International University, Malaysia
must have arisen from replication. Students also mentioned that as gametes pass down
information to the next generation, they should not have any information missing, and hence
should contain the complete set of pairs of homologous chromosomes.
Student Understanding of the Chromosomes Relationship to the Amount of DNA
Diverse understanding of this concept amongst both groups of students is revealed by varied
responses to related questions which occur with high frequencies (Figure 3). Such high
percentage (>30%) of alternate understanding in this concept has also been reported by
Marbach-Ad (2001) and the AAAS Project 2061.
Figure 3. Responses to questions testing chromosome - DNA relationship among A-level
students and biology undergraduates. (Pre-Instruction)
Student responses and focus group discussion revealed that students think that;
 A single replicated chromosome consists of a single strand of DNA.
 A homologous pair of chromosomes has one DNA molecule.
 Having a diploid set of chromosomes means the chromosome has been duplicated or
replicated.
 Chromosome number and DNA content double together.
 A chromosome has hundreds of DNA molecules
Focus group discussion revealed that there was confusion between the double stranded DNA
molecule which is an innate characteristic of DNA, and the double stranded or X-shaped
chromosome which resulted from replication.
Although not mentioned by our students, Kindfield (1991) noted that students think that
chromosomes have an X-shaped structure due to joining of homologous chromosomes
contributed by each gamete upon fertilization.
As Polachek et al. (2008) noted, students are misled into thinking that the replicated
chromosome is the normal form because of text book diagrams. These diagrams do not show
the chromosomes in the interphase nucleus (as it cannot be seen under a light microscope),
and the first time students observe the chromosomes in text book drawings is in the double
stranded or X form with two chromatids. Our students moreover stated that since the two
arms of the X-shaped structure are joined together at the centromere it should be a single
entity and thus consist of one single molecule of DNA.
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Proceedings of the 3rd International Conference of Teaching and Learning (ICTL 2011)
INTI International University, Malaysia
In addition we propose that this relating of the X-shaped structure to the normal, prereplication state of a chromosome is compounded by the so named X-chromosome. Our
students mentioned that they expect an X-chromosome to be X-shaped, and not linear as it
actually is. And with the X-chromosome being X-shaped, all other should follow suit.
The next step in student logic is that if an X-shaped chromosome is a single entity, replication
will turn it into two X structures. This in turn leads to difficulty among students on changes in
chromosome number and amount of DNA in the subsequent events of nuclear division.
The selection of the option, “A chromosome had hundreds of DNA.”, on the other hand was
due to confusing the polymer, deoxyribonucleic acid, with the monomer
deoxyribonucleotide.
Student Understanding of Haploid - Diploid Number Concept
A-level students and undergraduates responses to question addressing this concept showed
high percentages of incorrect option selection (Figure 4) confirming the difficulty of this
concept as has been reported (Kindfield, 1994; Dikmenli, 2010).
Figure 4. Responses to questions testing understanding of haploid versus diploid concept
among A-level students and biology undergraduates (Pre-instruction).
Looking at the incorrect answers selected, student believe that the;
 Diploid number is the number of paired chromosomes. (That is a pair is one)
 Diploid number is the number of sister chromatids.
 Diploid number is the number of cells in the body
Focus group discussion, lead us to construe that following student logic, since di- means two,
a diploid number should result from replication. Subsequently, if the chromosome is
replicated there should be chromatids present, so the diploid number should be the number of
chromatids. The other alternate concept where students related diploid to the number of cells
arose from misunderstanding references to “diploid cells” or “haploid cells”.
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Proceedings of the 3rd International Conference of Teaching and Learning (ICTL 2011)
INTI International University, Malaysia
Post Instruction Results
With non-targeted instruction, the undergraduate (n=17), only showed significant difference
for Question 36, while the A-level students (n=99) showed significant improvement on 8 out
of the 20 questions at P<0.01. Consequently these misconceptions still need to be addressed.
Limitations of Study
There is some concern regarding students’ sincerity when responding as there was no credit
given for answering the questions correctly. In addition, the sample size was still fairly small
CONCLUSION
Our concept assessment is a work in progress, but has yielded some useful information. Our
data corroborate others (Lewis & Kattmann, 2004; Saka et al., 2006; Dikmenli, 2009)
demonstrating that alternate understanding of basic genetic concepts remains in different age
groups. Furthermore, the study sheds light on student logic which leads to student
understanding.
The research results imply that educators need to target teaching to difficult concepts. Thus
we continue our inquiries into obtaining clear test items that measure conceptual
understanding to formulate targeted teaching techniques. Anecdotally students mentioned that
the discussion of the instrument questions and student ideas was effective in building their
understanding. This suggests that the questions can be used as tools to confront students with
their own understanding and to initiate dialogue to re-conceptualize their ideas.
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