Central Dogma Activity Modifications after Fall 2014
The last version of this activity emphasized the effect of different types of mutations on the steps
of the central dogma. Student performance on clicker questions about the different types of
mutations indicated that there was strong understanding of mutation types (i.e., what is a silent
mutation, a missense mutation etc…) with less understanding of how these mutations affect
replication and transcription. As a result, the activity was modified: clicker questions that the
majority of students answered correctly were removed and questions specific to the termination
of replication and transcription were added.
Several faculty members discussed the benefit of a homework or worksheet assignment to enable
students to synthesize the concepts. A draft homework assignment is attached to this document.
Interested faculty are encouraged to provide suggestions, comments and ideas. These homework
problems are derived from the faculty-generated exam question list that was compiled in the fall.
Please return edits, comments, or suggestions on the homework and/or activity by XXXX.
Formatting Comments
– Animation was removed from the majority of the slides except for the appearance of the
questions.
– Topics in BLUE BOXES on slides are prompts for general discussion in the classroom.
Specific Modifications
– Black borders have been added to the slide that illustrates the location of the 5 nucleotide
differences to show that the 5th mutation is within the gene and not at the end of it (slide
5).
– Clicker question relating to gene structure has been replaced with this discussion prompt:
“Based solely on these labeled features, discuss which of the DNA differences would be more or less
likely to result in the phenotype of muscular dystrophy?” (slide 6).
– Clicker question relating to the impact of a silent mutation has been replaced with a
discussion prompt: “This type of substitution (a silent mutation) results in the same amino acid,
and therefore protein. The results from other mutations are more challenging to predict…” (slide
7).
– The first clicker question (slide 8) now asks about a missense mutation that changes asp
to glu. These amino acids are similar in structure. Several students at UMaine asked
questions about amino acid structure, so an additional slide (slide 9) comparing the
structure of all amino acids and clearly illustrating the similarity of asp and glu has been
added to enable further discussion.
– One of the two questions relating to a possible mutation in the promoter has been
removed leaving one that uses data to predict outcomes of a mutation in the promoter
region (slide 10).
– Clicker questions and slides that were removed from the first version (e.g., the learning
objectives) are now in a separate file (also attached).
Changes specific to the central dogma
Student performance slightly increased in two classrooms that used the activity (Figure 1). The
pretest was given after the faculty members discussed translation and the posttest was given
after the activity was taught. Data from a class where the pre/post test was given but the
activity was not used is included for comparison (Figure 2). The modifications described below
were made to try to increase these gains.
Replication: Clicker data and observations from 4 different classes revealed that the question
asking if a stop codon would affect DNA replication split the class. To address this issue, after
this initial question, we have added a slide that asks students to discuss what role stop codons
have in DNA replication. Students are then presented with two additional clicker questions that
use models and diagrams to directly address how DNA replication is terminated (slides 13-15).
Transcription: The previous version of the activity did not result in a large improvement in
student understanding of transcription, suggesting this as an area for improvement. An
additional question about what is responsible for the termination of transcription has been added
to allow for direct discussion of this topic (slide 17). Students then revisit the question of how a
stop codon will affect transcription to solidify understanding (slide 18).
Translation: By this point in the exercise most students arrived at the correct thinking about the
effect of a stop codon on translation, so no additional translation-specific content was added.
The exercise is wrapped up with the final discussion of what constitutes a “mutation.” Students
chose a range of answers and faculty generally felt it generated good discussion. The last slide
can provide a segue from the case study back to topics in the class, for example further
explanation of X-linked inheritance, or the scientific method.
New Activity Summary: 21 Slides; 11 clicker questions
Q1: Missense mutation
Q2: Regulation of transcription
Q3: Data interpretation/ Regulation of transcription
Q4: Nonsense mutation + DNA replication
Q5: Modeling and DNA replication
Q6: Regulation of DNA replication
Q7: Nonsense mutation + transcription
Q8: Termination of transcription
Q9: Nonsense mutation + transcription (revisited)
Q10: Nonsense mutation + translation
Q11: What is a mutation
Aggregate Student Performance
Pre-Ac vity-Post
Correct
Mixed
Incorrect
100%
90%
80%
70%
60%
50%
40%
68
61
30%
54
56
Post
Pre
49
49
20%
10%
0%
Pre
Post
Replica on
Pre
Transcrip on
Post
Transla on
Figure 1. Aggregate performance of students (N=350) who answered the pre-AACR question
(after completion of translation instruction in class), did the in-class activity, and answered the
post-AACR question. Mixed responses could range from partially correct to irrelevant. Overall
there was improvement in understanding as a result of the activity.
Figure 2. Performance of students (N=400) who answered the pre and post-AACR question
during their course but the activity was not used. Mixed responses could range from partially
correct to irrelevant.