In the lectures and recitations this week, we are focusing on the Central Dogma

Question

In the lectures and recitations this week, we are focusing on the Central Dogma and molecular genetics.

For this discussion, you must reference the paper linked below by Wright (2014). Please read/skim through the abstract and introduction for context on the study. I would like you to focus on the open-ended assessments (figure 2 and table 3) and the student interview responses regarding the meaning of the arrow between DNA and RNA (interview dialog on pages 344 to 345 and sample explanations in table 4).

Wright_2014_ - What Do Students Think the Arrow Means.pdf

Wright (2014) discusses student misconceptions on the Central Dogma.  There will be two parts for this week's main discussion post:

Part I: Select one of the students' statements from either an assessment OR an interview in the paper and pick it apart. Which concepts did the student get right and where were they wrong? How would you re-word their response to better explain the concept? Try to think about it from their perspective - how did they reach that particular conclusion? (Please copy the student’s response from the paper here for easier comparison between their response and yours. For the longer interviews, please state the student's name only.)

Part II: Now you are the student being interviewed. Select a concept from the central dogma – this can be as general (replication, transcription, translation) or as specific (DNA proofreading, synthesis of the Okazaki fragments vs. synthesis of the leading strand, etc.) as you’d like. Please explain your chosen concept to the best of your ability.

Explanation / Answer

Part I: We will discuss the interview of student named Cory.

Interviewer: Describe to me what this figure means to you if you’ve seen it before, what do you think the big picture is here?

Cory: I mean it seems like since you made the arrow (points to the first circular arrow) like that it feels like DNA is a replicating process. Um—and then I’m guessing it’s more of a— to me it’s a reverse process because protein is made up of, I mean RNA is made up of protein and then RNA is

what makes up DNA. I think.

Cory repeated his idea that “RNA is made up of protein” and “RNA is what makes up DNA” several more times during the interview. To clarify his thinking about the arrows in the figure, the interviewer sketched a generic diagram of a metabolic pathway “A?B?C” and asked Cory whether he thought it was a comparable diagram. He agreed this new diagram was the same as Figure 1, suggesting that he interpreted the central dogma representation as a series of chemical reactions.

Cory is right in thinking that the first step in the Central Dogma is a replication process i.e. DNA is copied or replicated. He is wrong in thinking that proteins are made up of RNA and RNA is what makes up the DNA. He is thinking of Central Dogma a series of simple chemical reactions is also wrong.

Now we will try to reword his response and explain Figure 1 in the article.

The round arrow over DNA represents that the information contained in DNA is copied or replicated in the first step. The second arrow between DNA and RNA represents the transfer of information from DNA to RNA i.e. a copy of RNA is transcribed from newly replicated copy of DNA. The third arrow represents the transfer of information from RNA to the protein i.e. the information from newly transcribed RNA is now translated into a protein.

Thus, Central Dogma is not simply a series of chemical reactions but it is a sequence of flow of genetic information from DNA to the protein through an intermediary known as RNA.

Part II: We will try to explain "transcription" in Central Dogma in our words.

Transcription is represented by the first (straight) arrow in the graphical representation of Central Dogma. It is the synthesis of a copy of RNA from a segment of DNA which replicated in the first step (shown by round arrow in the graphical representation of Central Dogma). Transcription of a copy of RNA from DNA segment is facilitated by enzymes such as RNA polymerase and transcription factors. The final product of the transcription process is more specifically known as messenger-RNA or m-RNA, The process of replication of DNA segement and transcription both take place in the nucleus of the cell.

Thanks!

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