Meta-Reflection on Assessment

6. The teacher designs student assessments around clear criteria and standards to evaluate student learning and provide feedback to students. Teachers that continuously assess students per clearly-defined learning targets and provide high quality feedback will be able to modify their lessons and improve instruction so that learning is more effective for all students [1].

The learning target for this learning segment is that students can describe the structure of DNA and its function and explain the major steps of the processes of DNA replication, transcription, and translation. The learning target corresponds to the overarching NGSS Life Science standard:

HS-LS1-1. Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells. All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells. 

First, students learned DNA structure & function and the major steps of the process of DNA replication. To assess students for their extent of grasp on the learning targets, the formative assessment of students building a DNA model out of paper, using glue, markers, and other craft supplies promoted further student understanding of the structure of DNA and the major enzymes as well as their function in DNA replication [1]. The grading rubric required that students had to demonstrate the following elements: 

• The ends of the four complementary strands of DNA—two original and two replicated strands—are accurately labeled with 5’ or 3 (4 points);
• The strands are shown to be antiparallel in the nucleotides of one single-strand of DNA appears to be the upside down relative to its complementary strand (2 points);
• Major enzymes Helicase, DNA polymerase, and Ligase are correctly drawn and its role indicated on the model (3 points);
• The three major components of at least one nucleotide—phosphate group, sugar, and base—are accurately labeled (2 points);
• Analysis questions about DNA structure and replication (5 points);
• Nucleotides are arranged so that correct complementary base pairings of adenine (A) with thymine (T) and cytosine (C) with guanine (G) is shown (2 points);
• The direction of DNA replication of the leading and lagging strand is correctly indicated on the replicated strands with arrows (2 points).

Figure 1. DNA Paper Model & Analysis Grade Distribution. The total number of students in class is thirty. Students completed this formative assessment in groups of three students.

Figure 1 shows that 70-percent of students in a class of thirty-students scored at least 15 points out of the maximum score of 20 points. This reflects that most of the class attained a general understanding of DNA structure & function as well as the major steps in the process of DNA replication [3]. After instruction on DNA structure, function, the process of replication, the students moved into learning transcription and then translation. For assessing the students’ progress in learning and effectiveness of scaffolding the information from DNA function and structure to replication, transcription, and then, finally, translation, I administered a summative assessment with a formative assessment in the form of puzzle to especially engage and entertain the students. The assessment—called “CHNOPS Lab Activity”—consists of four (4) questions that evaluated student grasp of the following success criteria:

1. Student cites three macromolecules that are composed of the six elements C, H, N, O, P, and S (e.g., DNA, RNA, proteins): 2.5 points.
2. Student must use the academic language to generally describe the three major steps of how DNA forms proteins: DNA is transcribed into RNA in transcription that occurs in the cell nucleus; RNA leaves the nucleus and is then translated into a chain of amino acids on a ribosome through the process of translation; the chain of amino acids then folds into a protein—to earn the full 2.5 points;
3. Students demonstrate understanding that the type of mutation and where it occurs (e.g., DNA, RNA, or amino acids) determines the magnitude of effect on protein formation are given a total of 2.5 points;
4. Students showing understanding that several codons can code for the same amino acid, therefore allowing for point mutations to have no effect on the protein formation further down the Central Dogma of Molecular Biology scheme are given a total of 2.5 points;
5. Finally, students that transcribe and translation all the genes in the activity so that they can generate their unknown mythical creature are given a total of 5 points [2]. 

Out of a class of thirty students, 80-percent of students scored at least 80% and half the class scored 93-percent or better on the assessment [3]. Figure 2 exhibit the summative assessment of focus. 

Figure 2. CHNOPS Lab Activity. A summative assessment of success criteria and standards for learning segment on DNA structure, function, & processes.

Table 1. CHNOPS Activity Grade Distribution. The maximum points for the summative assessment called the CHNOPS Activity is 15 pts. The total number of students in the class and submitted the assignment is 30.

The first question (I) of the above summative assessment asks students to list six (6) chemical elements essential to nucleic acids: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. The question prompts students to realize the structure of DNA contains phosphorus—found in the backbone composed of phosphate groups and deoxyribose sugars, nitrogen—existing in the nitrogenous bases of the nucleotides, and carbon, hydrogen, and oxygen—found throughout the composition of DNA, RNA, and proteins. Since most of the class missed the question entirely, this question informs me that the students do not, as further confirmed, have a rudimentary knowledge of general Chemistry [5]. The famous cognitive development theorist Lev Vygotsky calls for learning to be within students’ zone of proximal development—wherein guidance and scaffolding from the teacher adequately challenges but not overwhelm students in a way that results in them not being able to provide answers to questions that probe for evidence of learning. For my students to make progress toward the zone of actual development—wherein they can think and problem solve independently—I think teaching this class the basics in Chemistry would be an appropriate use of assessment results to inform further instruction so that learning is more effective for all students [6].

The second question (II) of this assessment encouraged students to practice the academic language of this learning segment in that student responses should contain correct usage of academic vocabulary (e.g., transcribing, transcription, translation) in explaining that DNA is “transcribed” in the nucleus through transcription, producing an RNA molecule that leaves the cell nucleus and arrives at a ribosome to become translated into a protein through the process of translation [5]. The whole class demonstrated the correct scheme of transcription first occurring in the nucleus and translation occurring later to ultimately form a protein. Although, the student—whose work is depicted in Figure 2—correctly described the order of events, she failed to mention the names of the processes—transcription and translation, so she only received partial points. The overall class’ answer to this question reflects that of the student whose work is depicted in Figure 2 in that most students’ command of the academic language is insufficient in demonstrating a firm understanding of how DNA codes for proteins per the Central Dogma of Molecular Biology. Seeing more movies and animations made for the processes of course provides repeated exposure to the components (e.g., enzymes, molecules, etc.) involved in the processes, their scientific names, and the names of the processes. In Brain Rules (Medina, 2014), Medina proposes that better learning is achieved when more senses are stimulated at the time of acquisition. When there is simultaneous stimulation of two or more sense—called multimodal reinforcement—each individual sense is magnified. For example, referred to as the Proust effect, a memory of any sort is enhanced when its learning occurred with a smell(s). Richard Mayer, cognitive psychologist who has spearheaded the study on the relationship between pictures and on learning from reading, finds that “students learn better from words and pictures than from words alone” (p. 175). I think enhanced frontloading of the material will enhance command of the academic language and improve communication of learning content [6].

Moreover, the fifth question or section (V)—which the grading rubric allotted five-points—was a formative assessment of students’ understanding of complementary coding of nitrogenous bases from DNA, to RNA, and, finally, to amino acids. Overall, all students in the class showed complete understanding on complementary base-pairing of DNA and RNA that eventually codes for a chain of amino acids through correct matching of codons and anticodons. Figure 2 demonstrates assessment results of one student that is representative of the overall class. Based on the assessment results as shown in Table 1, I inferred that students sufficiently hit the cited learning criteria and standards for this learning segment [4].

References

Medina, J. (2014). Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School. Seattle: Pear Press.